I don't really like the term, seeing as there's a ton of pejorative aspects attached to it in the West. Sedate or moderate Anime watchers tend to end up picturing obsessive fixations on body pillows with Moe eyes and, well - there's freaking *Real Life Girls*, out there. Motoko Kusanagi isn't a "significant other", she's just a character I like following!
If I had to play along, though, and admit that some concepts and characters have triggered a protective streak or a bit of fondness in me, I'd have to name Fawkes from Fallout 3, and Dean Domino from New Vegas' Dead Money expansion.
Fawkes is a bizarrely cultured Super Mutant who really just wants to fit in and who sometimes feels like an overgrown and super-literate five year-old, complete with sudden quotations and general guiltless Berserker-worthy pleasure at blowing shit up. He deserves a hug and a similarly intellectual presence at his side to keep him stimulated, in the hopes that the FEV's progression to Behemoth status won't turn him into another dumb grunt.
As for Dean, he's an Old World crooner with severe trust issues, an unhealthy fixation on an old treasure and heaps of insecurities. His ego needs to be stroked with tweezers if you want him to stick by you without pulling a gun on you at the last second - and he refuses to consider the Courier's potential words of wisdom.
He's damaged, classy as fuck and burnt-out in the kind of glitzy, glamorous way that reminds me of Hollywood's old glories. He's fascinating and I hate having to ignore my own principles to make him happy. I wish you had the option to make him see reason *before* the heist is actually carried through.