1
2
3
4
5
6
7
8
9
Okami

Gaius and Rin: First going off, he was a normal guy. Therefore, an easy target. Easy to steal from. Easy to manipulate. Easy to play around with to get things he wanted without any real strings attached. Someone he could drop and forget about whenever it was most convenient for him. A thief's life is like this, after all, they wear out their welcome rather quick.
But it's a bit hard when people don't take the warnings that befriending a thief is a bad idea, because that means you start giving a damn about people who were once just targets.
While he and Rin aren't TERRIBLY close friends, they're still close enough that Gaius would probably protect Rin's life if it came to it, both because of Rin himself, and because of Gaius' close friendship with Drei. If you're important to him, then you mean something to the thief, that's just how things work.
Getting to know Rin better... is probably something that'll develop over time.

Gaius and Severa: Out of all of his 'Kids', she's the only female, and she's the only one who got the idea that Gaius is just a kid himself, and being a father isn't something that comes naturally to him. He's still growing as a person, and being expected to be the 'father' those from the future remember just isn't something he can promise, and Severa is one of few who actually understand that. However, being that they are related, he still feels obligation towards her. To a point where he would probably give his own life to save hers if it ever came down to it.
In a place like Mafia where such isn't necessary, however, he'll just live his life in the city doing something an apparent version of himself couldn't: and that's to just spend time with her.