Thanks for the reaction. It would be really cool if you watch OVA 1 before season 2. It explains in detail how Ogata joined Hijikata. Also, if you want to follow the chronology of the manga, you should watch OVA 3 after OVA 1. However, the series has already connected the events of two seasons, leaving out the plot of OVA 3, so you can watch it later if you want.
Of course, it's a bit weird that OVA 1 and OVA 3 are related to season 1, OVA 2 and OVA 4 are related to season 2. But I think the anime creators had their reasons for doing so.
P.S. Sorry for my English, I'm still learning it.
