Spoiler for OVA bundled with Volume 13 of the novel:
I had a look over the episode and it contained three stories; each dedicated to the Takanashi sisters. We start off with Sora's story, which was arguably the most fanservicey part, and involved her being accidentally trapped in the closet with Raika (Miu unintentionally caused them to be locked in the closet). She almost had her first kiss with Raika (!) in the closet, but Yuuta walks in on the naked duo just as they manage to get out of their predicament.
Special mention to the anime debut of Kitahara Shiori, the next-door neighbour of the Takanashi family. Iguchi Yuka does a nice job voicing Shiori here, and she gets joint-focus with Miu on the second part; she makes an appearance in all three stories though. We start off Miu's with her making a mess by falling face first into a cake Shiori brought over, then the bathe scene. Miu's story was just as fanservicey (lots of dressing up here), and we get to see Shiori's wild imagination (which is a defining trait of hers, apparently). Towards the end she imagined herself as Segawa Shiori, revealing the extent of her crush on him.
The last part was the most adorable and no fanservice here. Hina goes out on her own in the rain and the whole family went searching for her, fearing she might be lost, but she is eventually found by Shiori at a nearby playground, and they eventually reunite at a giant ferris wheel. Hina gets chided for making the family worry about her, but she is forgiven in the end. The end was somewhat heart-wrenching as Hina appeared to know that her parents weren't around anymore and everyone else was brought to tears by it, inside the ferris wheel.
It was a fun ride, this episode. Yuuta for once is out of the focus for large periods, while the sisters get their time in the limelight. I will look forward to a second season of this, if that ever happens.