Star Ocean

Star Ocean is a series of JRPGs spanning several console generations with a couple of spin-offs and adaptations. Heavily inspired by Star Trek, each story features characters from a variety of worlds and cultures working together. The mainline games also include rich item crafting and relationship systems, though the depth of the implementation varies.

In college, I picked up Star Ocean: The Second Story from a used game store on a whim and totally fell in love. While the games have various strengths and weaknesses and are certainly not all the same level of quality, I'll always have a soft spot for this series and a lot of that is down to its lovable characters.

Waifu Tier
The best of the best. Only one character may be in this tier for a given work or medium. This character... is Mai Waifu.

Imouto Tier
From the Japanese for "little sister", characters at this tier are not love interests in the romantic or sexual sense, but are characters that make you want to protect and nurture them.