There isnt really any new information. You're right that its mainly a way to inform newcomers on Takeru's character and emphasize Mikoto's fear and guilt over what happened.

Oh interesting. Well his involvement in the Miyuki Shiratori arc probably gives us even more backstory to the "lewd demon bugs" lol. Will be cool to get more of that figured out someday.

It occured to me that, if the next chapter I'm writing is going to be about Kikuka and Ouka, I should probably have a better handle on their characters, and since the sum total of their characterization in the OVA is "more stoic than the regular trio before getting mindbroken", I should probably ask what they're supposed to be like as people, which would also help going forwards if I write anything else involving them.

There are some doujin I can find where they show up, but I don't trust those to give me much more than the OVA.