This OVA for Astarotte no Omocha contains two portions. The first is just additional fan-service with Asuha's class assignment being studying everyone's panties. The second part retells some of the history of how Naoya met Astarotte's mother (and thus supposedly how Asuha came to be...). This is an add-on that should be watched after the parent story, if you so choose. The animation and sound are identical to the original, you still get marginal ecchi though with the second part you do get some partial nudity on Mercelida. Story is divided as the first part is pure fan service while the second part actually helps clarifyNaoya and Mercelida's past, though it's also a bit creepy as Naoya looks way beyond underage...

It's a short 30-min watch so if you liked the original then you'll enjoy this as well.