@RandomFanguy
If he laughs really hard or celebrates with a lot of emotion that is so unlike his stoic face since they met she might be surprised, and if she got kinda irritated looking at him celebrating she might get mad and start saying stuff like : "Are you that happy beating me!!" or "Don't think you are better than me with one win"
at that time he suddenly becomes serious and say "I love you, Let's get married" she would be stunned and freeze a bit, then he leans in with a simple kiss on the cheeks are soft hug then
Scenarios are flooding my brain right now and I ca't stuff the fluffly what-if scene when it happens.
At the rate they're head over heels and at the rate his shogi skills are not improving they're going to get married without him ever admitting he's in love with her.