It's actually occurred a lot in real life that a couple doesn't have emotional support anymore after years of wedding even without an act of cheating. His dad chose to give up on that ties which is his dad fault of course. Maki's reaction is normal even with the fact his dad want to support him as his biological dad. As a child in his family, maki just want a normal dad and normal familySo basically this little arc concluded with the dad deffo had an emotional affair at work whilst married cause he would’ve said it straight up and mc has deal with his bs
His mother should get a new father for him so his biological can go live with regret or just moving on