It really happens, mika confirmed the event in chapter 61 is indeed happen so this must be the continuation from that point. Also the dialog between him and his wife best friend when she said "you used to be so skinny back then" is a dead give away.
Oeda looks cute with the new haircut, she looks much younger. Also, did everybody realize that Elfuda new hairstyle is the "housewife cut" from naoe dream sequence?
I think, it could go either way from here :
1) just like you said, okumura realize his feelings and Mikari wins
2) okumura realize acknowledge his feelings that he indeed loves Mikarin, yet he realize it too late and know fall in love with lilisa. While Mikarin accept that and finally move on...
Unfortunately i think you're right, my prediction maybe okumura with lilisa and Mikarin with tsubaki (well, since yuri is not out of options). But i still had a little bit of hope. The thing is there's so much build up about mikarin long time crush on okumura and okumura sorting out his feelings...
This extra chapter is shit and unecessary, i can't argue with that. But i think it happened before that last chapter confession, cause this story happened during the summer holidays, while the confession happen after the summer holidays.
Really girl? After all those dirty minded flirtatious premiscuous attitude you show and your strong desire to had sex with him and now you backing up because of a forhead kiss?