So far it's only based on a few hints people have noticed such as Shimamura willingly arriving half an hour early at her date with Adachi and covering her chest in the swimming pool's changing room. It's possible she hasn't simply been able to brush off what Adachi told her over the phone.
While her unusually early arrival could simply be explained as her not having much else to do (we all know how much Hougetsu puts her free time to good use, after all), yeah, the swimsuit thing is suspicious. She reeeeally didn't seem to do that the last time she went to the pool; as I remember it it wasn't that clear, and I could buy it if it turned out there was nothing peculiar about her having her swinsuit under her clothes, but it seems unlikely.
As other evidence that she's acting strange, there is whatever she wanted to tell her in the last chapter, and her saying to herself "what is this?" when she met Adachi for their date, which the latter believed to be about the whole situation, rather than the flowers.
last edited at Mar 5, 2020 9:59PM