Well... You could bring him something. ... even if you're not sure what he likes. [He makes a thoughtful noise.] If you like cake, take a couple pieces to him and say, 'This is something I really like and I thought you might want to try it.' Then you can spend time with him sharing it.
As far as doing target practice... if you want to learn, you could ask him to teach you. That's the sort of thing I like doing for my friend, letting him teach me about things he's interested in. Even if you're not, you could ask to watch.
[With all of this, Souji's starting to feel like he's turning into Ian. He's not sure he's ever talked this much to someone outside of his team before, especially with giving advice, but... if he can share what he's learned from being with Ian and himself, then that's good. Right?]
I used to be really closed off, too. Not because I lost anyone, but... I know those are things I would have liked. The worst he can do is say no, but he'll at least know you're thinking about him.