Asumi is a third-year student at Aiho school. She is Yusuke's childhood friend and they attended the same grade school. She would bully Yusuke and she freely lets her fists fly at him when she is angered. Asumi attends the same class as Tomoe and Marumu and also shares the same room at the Harukaze dorm. She declared herself their leader. She calls Tomoe "Moe-moe" and Marumu "Marutan" and insists that they call her "Asumin".
Asumi loves life and enjoys living. She is incredibly energetic and she hardly sits still long enough to think things through. Her motto is "Youth is short, live it to the fullest and have no regrets!". Asumi loves okonomiyaki and her favorite is buta tama (pork and egg).
Asumi once had an older sister, Asuka, but she passed away when she was young. Asumi promised Asuka that she will live her life to the fullest.
Asumi and Yusuke attended the same class. She used to bully Yusuke. One day in class, Asumi snatched Yusuke's compass. Yusuke fought with Asumi to reclaim the compass. Asumi suddenly started acting strangely and Yusuke brought her to the nurse's office. On the way, she lost control of her bladder and relieved herself in the hallway. Fortunately, no one saw her. Yusuke cleaned up after her and Asumi demanded that Yusuke never reveal that ordeal to anyone else.
Asumi and her family moved out of town when they were in 6th grade and they lost contact with each other.
First Year of High School
Detailed in Episode 19: Then the Three Met.
Asumi was assigned to share a dorm room with Tomoe and Marumu. She was frustrated by their difference in personality. A month later, Asumi requested Yagami for a change of rooms but Yagami explained that dorm room occupancy were arranged only once a year and that occupant transfer cannot be done.
Asumi tried to motivate Tomoe and Marumu to no avail. She then attacked them. Tomoe and Marumu eventually fought back and their hair got messed up. Asumi was content and gave them yellow hair ornaments to fix their hair. She explained that yellow is the color of happiness. They became close friends ever since.
Heart de Roommate
Asumi was chasing after a panty thief. She discovered Yusuke sprawled on the sidewalk exhausted and she delivered a flying kick to him, knocking him out instantly.
Episode 1: The Beginning
Asumi eventually found the real panty thief and gave him a flying kick. She returned and apologized to Yusuke. Yusuke explained his situation to her. Asumi introduced herself to Yusuke and she remembered who he was. She decided to take Yusuke in, and in return she wants Yusuke to keep her secret safe, though Yusuke had forgotten what that secret was. Asumi had Yusuke sleep in the closet.
Episode 2: Transformation
Asumi decided that Yusuke shall dress as a girl to travel between the dorm and school. Tomoe helped him dress up. Asumi calls Yusuke "Parasite One" and held a welcoming party for Yusuke at Okonomidama, an okonomiyaki restaurant.
Episode 3: The Name is Toshibo
Asumi was shocked to discover Toshibo at the dorm room. Tomoe revived it and Asumi accepted it into their circle of friends, calling it "Parasite 2".
Episode 4: Emergency Meeting at the Hot Spring
Yusuke met Akane, Kaoru, and Midori. They advised Yusuke to not mix with Asumi and invited him to join them instead. Kaoru noted that Yusuke was rather tomboy-ish. Asumi declared a meeting at the Katsuragi Inn to plan to get back at them. She also told Yusuke to act more feminine to not raise suspicion that he may be cross-dressing. Asumi enjoyed the hot spring so much that she forgot what she called the meeting for.
Episode 5: My Savage Sister!
Asumi waited for Yusuke after school to escort him home. In town, they met Namiki. She mentioned that Yusuke was prettier than Asumi and Marumu agreed. Asumi became enraged at Namiki for that. Yusuke explained that Namiki was looking for him. Asumi decided to prevent Namiki from meeting Yusuke to keep their secret safe.
That day, Yusuke met Namiki in school. She wanted to meet Yusuke at his dorm. Asumi tried to distract her from reaching the dorm but failed. Namiki met Yusuke in town after school. She started flirting with him then discovered his identity. At the dorm room, Yusuke explained his situation. Namiki requested to visit the Katsuragi Inn and Asumi begged Tomoe to agree to it to buy Namiki's silence. Satisfied with her visit, Namiki returned home.
Episode 6: Code Name U-Suke
Asumi declared that Toshibo had been promoted to the rank of regular roommate. Yusuke was upset that it could be promoted earlier than he could. Marumu explained that Yusuke needs to put forth more effort. Tomoe explained that he will have to do something special for Asumi to get promoted.
The next morning, Asumi was frantically searching the dorm room. Marumu explained that she had lost an accessory. Yusuke knew what it looked like and spent the next 2 days searching for it to no avail. That night, Asumi discovered the accessory in her bag.
A week later, Asumi called for a celebration at the okonomiyaki restaurant. Asumi declared that Yusuke had been promoted to the rank of regular roommate.
Episode 8: Crash of the Titans! Asumi vs Namiki
Namiki declared that she had transferred to Aiho school and that she had got a dorm room beside Asumi's. Namiki invited Tomoe to live with her but Asumi disagreed, declaring herself leader of Tomoe and Marumu. Namiki questioned Asumi ability to lead and they engaged in a competition. Asumi admitted Namiki was superior to her.
Tomoe explained that she recognized Asumi as her leader and Marumu agreed. Namiki then forfeited the competition and declared herself Asumi's master to train her.
Episode 9: The Girl Under the Moonlight
During the holidays, Asumi read books on leadership.
Episode 12: Shaking Heart: Part 1
At the school rooftop, Yusuke saw Asumi talking to Misaki. Yusuke became jealous. She teased Yusuke about him being prettier than she was when he was cross-dressing.
After Yusuke accidentally kissed Tomoe, Asumi suspected that he was the cause of Tomoe's moodiness and confronted him. Yusuke tried to evade her interrogation by threatening to expose her secret. Asumi became enraged and beaten him unconscious. After the woke up, he rose up quickly and accidentally kissed Asumi. She slapped him and became infuriated. Yusuke ran away from the dorm.
Episode 13: Shaking Heart: Part 2
If Yusuke decided to confess his feelings for Asumi, he waited for her at the school gates. Asumi approached him and explained that she was waiting for him at the dorm room. She explained that he was allowed back to the dorm. Yusuke confessed his feelings for Asumi and she reacted badly. She confided in Yagami and she explained that Asumi may not be honest with her feelings.
Tomoe apologized for slapping Yusuke and explained that Asumi was sad when Yusuke left the dorm. Yusuke met Asumi on the school rooftop and explained that he discovered his feelings for her when he saw her with Misaki. Asumi kissed him and invited him back to the dorm.
Episode 15: A New Semester & A Transfer Student
Yusuke spent the summer vacation on the phone with Asumi. When Yusuke returned to the Harukaze dorm, Akane revealed her feelings for Misaki. Tomoe welcomed Yusuke and Marumu arrived during dinner. Asumi returned late to school the following day. Yagami introduced a transfer student, Hikaru. Asumi tried to approach Hikaru but she ignored her.
Asumi invited Yusuke to the school rooftop and declared that she wanted to keep their relationship secret from Tomoe and Marumu. After dinner, Tomoe asked about their plan for the future. Asumi declared that she simply wants to do her best at any given moment.
That night, Asumi invited Yusuke to town. They talked about their relationship and their future.
Episode 16: Love Storm
Yusuke remembered Asumi talking to Misaki and assumed that Misaki was interested in her. Yusuke confronted Misaki after school and he confessed his feelings for Yusuke. At the dorm, Asumi revealed that Misaki had asked her about Yusuke. She denied being acquainted with him but Misaki was adamant. Asumi then fabricated a fictional character around Yusuke's female self.
Since then, Yusuke became paranoid about Misaki. Misaki followed him demanding an answer. One day, Misaki discovered Yusuke exiting the men's bathroom in his girl clothes. Yusuke then brought Misaki to the school rooftop to reveal the truth. Misaki was shocked but quickly recovered.
Later, Yusuke and Misaki heard 2 girls talking about them being in a relationship. They confronted Asumi and she revealed that she started the rumor, insisting that it was half true.
Episode 17: One Fine Weekend
Asumi announced that she was going to school but Yusuke suspected otherwise. Marumu warned Yusuke not to pry to deeply into other people's secrets. Yusuke searched the school for Asumi but couldn't find her. At the Katsuragi Inn, he found Asumi and followed her to a cemetery. Asumi was honoring her sister's grave. Asumi found Yusuke in town and invited him for a date in town and the beach.
Episode 18: The Day the Earth Falls
Asumi told Hikaru a story about preventing the end of the world with the power of friendship.. Hikaru was unimpressed and left.
Episode 19: Then the Three Met
Asumi woke up with a bad dream about Hikaru. In school, Asumi tried to approach Hikaru but she ran away.
Episode 23: Fading Friendships
Yagami revealed to Yusuke that the boys' dorm recently had a vacancy. He hesitated with the decision.
Yusuke noticed that Asumi had been spending a lot of time with Hikaru. She would also act strangely and refused to explain her behavior to her roommates. One day in class, Marumu offered Hikaru a handmade yellow pin. Hikaru slapped it out of Marumu's hand and it shattered on the floor. Asumi then advised Hikaru to run away from the class.
That evening in the dorm, Tomoe confronted Asumi about the event. Tomoe demanded to know why Asumi didn't stand up for Marumu. Asumi still refused to explain her behavior but instead criticized Tomoe's goody two shoes and timid personality. Tomoe then revealed that she knew about Asumi's relationship with Yusuke and that she also had feelings for him. Tomoe felt that Asumi didn't trust her enough to be open about their relationship.
Asumi then slapped Tomoe and explained that she wanted Tomoe to tell her that earlier. They then traded slaps until Yusuke broke the fight up. Marumu voiced her anger at them and locked herself in her room.
Episode 24: Harmony of Minds
Yusuke identified Hikaru as the cause of the conflict and decided to confront her. He chased Hikaru to the school rooftop and found Asumi there. Asumi explained that she overheard the teacher's talking about Hikaru and decided to befriend Hikaru. He then explained the situation to Tomoe and Marumu.
Tomoe and Marumu decided to help Asumi to befriend Hikaru. Tomoe also requested Yusuke to forget her confession and promised to still be friends. That night, Tomoe and Marumu declared that they will help Asumi in her effort and they repaired their friendship.
The following day, Yusuke discovered Hikaru on the rooftop. Hikaru stripped naked and demanded sex from Yusuke, declaring that anyone who touches her will only get hurt. Yusuke noticed a cut on Hikaru's wrist and declared that he will not betray Asumi and left. Since then, Hikaru increased her interest towards Yusuke and the girls. Rumors spread about Yusuke and Hikaru on the rooftop. Asumi became suspicious about Yusuke.
The next day, Yusuke and the girls dragged Hikaru to the Harukaze dorm. Asumi declared that Hikaru will be staying with them from then on and Yagami revealed that Hikaru's lodgings had already been officially registered. Hikaru was assigned to Namiki's room.
Episode 25: Our Bright Youth
On graduation day, Hikaru was nowhere to be seen. Asumi and Yusuke discovered Hikaru standing on the outside of the guard rails of the observation platform. She was about to let go and Asumi rushed to catch her. Instead, Asumi flew off the platform and Hikaru caught her. Hikaru explained that her existence only hurt others and she was afraid of graduating and facing the outside world. Asumi shared her insecurities with Hikaru and her resolve to never give up. She also declared that Hikaru had already found the most important thing in life, friends. Hikaru broke down and returned to school.
They had missed the graduation ceremony. Yagami was upset but Hikaru voiced her desire to graduate with her classmates. Yagami then led them to the schoolyard where their classmates were waiting for them.
That night, Asumi approached Yusuke outside the dorm. Yusuke was surprised about Tomoe's confession but assured Asumi that he would still have chosen her over Tomoe. Asumi thanked Yusuke for his time with her.
Final Episode: Roommates Forever
Asumi declared that she will be furthering her studies to Greenland. Yusuke was upset that he couldn't be with her. Asumi promised to return to Japan for their one year anniversary. Yusuke promised to be a better man for Asumi.
The Place Where the Sun Sets
This episode is unlocked once Asumi's, Tomoe's, and Marumu's paths are complete.
8 months after graduation, Asumi decided to return home to visit Yusuke. They watched the sun set at the beach. She thanked Yusuke for tolerating her demands then passed out with high fever. Yusuke then called for an ambulance and she was rushed to the hospital.
Asumi explained that she was afraid of sleeping and never waking up. She took out her treasured accessory and explained that it belonged to her sister, Asuka. Studying at Greenland was Asuka's dream and Asumi wanted to live Asuka's dream in her place.
Asumi's parents explained that Asumi was born with a incurable fatal disease and the doctors predicted her life expectancy to only be a few months. Asumi bravely faced every single day with full knowledge of this. Asumi felt blessed with a life and explained that Yusuke had been an inspiration for her. Yusuke stayed at her bedside to her final moments.