In chapter 29, Shion's girlfriend Kana praises how good Aikawa looks in a wedding dress. Shion sadly looks aside and asks if Kana would like to wear a wedding dress (read: "go straight" and marry a guy) someday as well. Kana's response? "I'd like to wear one with you someday."
In Chapter 41, Aikawa's reaction to Maki giving him a Christmas gift. It's enough for Maki to finally admit to himself he does have feelings for Aikawa as more than friends.
The final chapter. Maki realizes there's nothing actually wrong with two guys dating and finally admits his love to Aikawa. And everyone else's response is calm acceptance with a simple, "Took you long enough."
Maki has a lot of unintentional romantic moments with Aikawa, and when pressed says it was just "natural" or nothing special. Such protests often only enhance the sheer sweetness of the moment. As Aikawa puts it, he is such a ladykiller.