This chapter feels kinda out of place, while I could understand with friendzoned childhood friend being wierd around her the enlightenment vs all of them when youngest has been overtly for him and tomboy has been semi overt this change he has had makes no sense.
For me it kinda makes sense. He was overwhelmed by the whole situation right from chapter one. His sense of "overtly for him" is totally off by then. Remember Shio snuck in and slept with him in the same bed, while pretending it to be a normal game for childhood friends. But yeah, in that case his reaction towards his long term friends should be a little bifferent from the "new" girls. The thing is, and I swear it's that, he's a douche who doesn't want to sour his relationship with any girl, by him by picking one.
I concure with you on, that deadlock between Shio and Akira also expanding on the other two too, is stupid. He should just have Ewwyu-zoned Shio and Akari, maybe put up a border for Littlesis, to make clear he isn't into incest play, and checked out Sportsgirl. But that's just my opionion. I guess he thought about everything, steeled his heart and put up that Ewwyu mask. Including all 4 of them into this might have been bad timing on their side. His decision to end it all with all 4 girls might have been in the spurt of the moment, as those have been the girls, that clung to him under that tree, which might have stressed the f*ck out of him.