オレの妹は思春期で発情期～ぬるぬる混浴温泉でしっぽりズッポリ？

"Ah! Mm! Big brother...Mn!, It's hitting my insides...!" I ended up going on a trip to the hot springs alone with my stepsister. In the night bus to the Japanese inn, I saw her boobs through her shirt, they pressed against me, and tons of erotic events!!? I... could probably die happy. We arrive at the inn the next morning, enter the hot springs, but w-w-w-wait, is that my sister completely nude!? The floor is slippery, I thoughtlessly slipped completely between her legs!?!? My cheeky sister is just so cute, I... I just can't help myself anymore!! (Source: Bevy, translated) Notes: Originally released in 84 episodes, reworked into 75 episodes on other platforms, and later sold as 28 chapters.