I feel like Kaoru genuinely "forgot" the events up until the accident in the beginning of the chapter. "Forgot" as in, it was probably being repressed and some part of her subconscious mind was still aware of it (hence her odd reactions such as trying to change the subject by telling Reiichi she lost her memories immediately leading up to the accident and her clenching her bedsheets when he left).
Looks to me like the floodgates were burst open when Uta gave Kaoru her smartphone back. We see that at first, Kaoru confuses the events when she mentions that she must've been with Risako at the time of the accident, but she ultimately remembers that it was actually Reiichi that was with Risako.
I think Reiichi is most likely cheating. I gave him the benefit of the doubt at first, but honestly, it was his birthday on the day he said he was going to be delayed by a few days coming home... but he ended up spending his birthday with Risako of all people.
Although, we still don't know what Reiichi sent Kaoru right before she fell.
last edited at Dec 26, 2017 6:25PM