I feel like if Akari and sensei ended up together, then Akari would end up having to deal with sensei feeling insecure a lot..........he'd be present a lot more, but they'd have to work harder on the emotional side of things. In that area, sensei kinda reminds me of Akari's dad OTL but like, not a Complete Piece Of Garbage. I don't think sensei would ever cheat or abandon his family, but he does has some emotional hang-ups that he should deal with
With Shimada, the issue is more about how little time he has for things besides shogi. He's self-assured and accepts himself, but as part of that he puts in an outrageous amount of work into shogi. With them I see it more like they'd both be super busy during the day, but usually they manage to spend time together at the tail end of the evening
For sensei and Akari, it seems like it'd be a rocky start that would end up really solid and good for both parties. For Shimada and Akari..............it seems like it could only work if they slide right into the "we've been together so long that we don't need to spend all our time together" phase. Like, I have no idea how they'd start dating, I can only imagine them years into the relationship