It looks more like the uke was crushing on him all this time (25 years) and the seme hasn't been able to get it out of his head since that incident 22 years ago when he discovered the ukes feelings because of the sleep kiss. Since then he's gone on as usual, dating women and even getting married, while trying to come to terms with his friend's feelings. Now he's 42, he's tried women and even marriage, now he's willing to give his friend a shot. I'm thinking you're right in saying the seme is in love with the uke now too (as evidenced by the jealousy and him even trying to talk the part timer out of it), but i don't think he's been crushing on him for years like the uke has, i think he allowed himself to give it a shot when his marriage ended in divorce. I guess we'll see? I could see it being that he's had a crush since the sleep kiss, but if so why not date? It'd be a plot hole. Maybe it's one of those guilty crush plots where he denies his feelings and dates women?
they both blushing peaches in the manga cover, i hope they didn't drag this on for 25 years to find out that they've actually been mutually pining for each other T^T all those wasted years when you could've had sex and youthful stamina!