Source(s) on Sasami experiencing her first period (OVA 2)?

[DishonorableKnight]

This is a specific question I had while rewatching OVA 2 that I need help answering. Basically, it's speculated that the first two episodes of OVA 2, "Hello Baby!" and "Sasami and Tsunami" hint that Sasami recently experienced her first period. It's not something that's explicitly said, and it's not something that I picked up on while watching, but that seems to be the explanation that goes around for why Sasami acts weird in these episodes (particularly "Hello Baby!" where Sasami basically sits in her room for most the episode). I asked Nonsuch Ned if this was something maybe covered in one of Kajishima's doujinshi, but he didn't know. Does anyone know anything about this topic or where I should be looking?

[shades of blue]