I've got an Azurill that's maxed out with five hearts from Pokémon-ami, and he's still not evolving in to a Marill. I've leveled him up since then, too, and he's still not evolving. Any ideas?

Through the power of love. You can't just take and take and take but you also have to give as well, it has to be a two way street. Oh! you mean in the game, that I do not know.

Magic.

Is that heart bar directly related to the old friendship stat that got adjusted from walking and leveling up? I know I got a soothe bag from the super training games so that system must still exist in some form. It probably is but maybe you have to raise the stat traditionally too.

Side note: This is like my 3rd pokemon game and the first time playing one that was brand new. I thought that strategy guide info would have just answered everything. It's cool to see people trying to figure things out together.

Pokemon-amie has affection, which is a different mechanic to the old friendship stat. You just gotta do it the same way you do in other games.

Patience. Lots of patience.

Ffffuuuuuu... I wasted so much time in Pokémon-ami...

Since pokémon don't follow you while you run around in-game, what are some tips for gaining friendship, then? I've wasted way too much time on this Azurill to not evolve it.

They gain friendship by being in your party and leveling up. They lose some when fainting. Also according to Reddit:

Why you should care about affection:

• +20% boosted EXP gained after every fight
• +10% evasiveness in battle
• Higher critical hit chance (battle text will say "Pokemon XXX is in sync with TrainerName" before critting)
• Your pokemon has a high chance of shrugging off status effects by itself (paralysis, burn, poison) after the end of a battle.
• Affection-based moves will deal maximum damage (Return, noticeably.

Not sure about that last one since Return was based on friendship before, but either way, not wasted time at all. I started getting boosted XP and I only have 3 hearts.

Right on, thanks so much. I'll keep plugging away. Cheers.

@nickdynmo Do you know if you got anything cool for maxing out the hearts? Any cool animations or anything?

Make sure he don't faint. Or just check serebii.net

Much higher crit chance, I think higher dodge chance, boosted xp.