Kenji and his friends are horny with Eru, a sexy older sister with a nice body who lives in the same apartment building. Eru shows off her sexy clothes as if to provoke Kenji and the others. One day, it rained suddenly and Eru came to Kenji's house, feeling drenched and forgetting his house keys. He wanted to take a bath to warm up his cold body, but he couldn't resist and peeked in...