Jyunichi is a lieutenant for the Ronin gang in Saints Row 2. Jyunichi is the person responsible for the death of Aisha. He's also the person who stabbed Johnny Gat.
Jyunichi is a very large character, and wields a Katana sword. In one of the Ronin missions, the player is tasked with killing Jyunichi. You fight him in a Japanese restaurant with a sword of your own.