Koneko-Chan, Kocchi Ni Oide. Since graduation from high school, Yuuko finally operated a clothes store. She hasn't had time to focus on her personal life since her job is going well. She's one day out partying with her best pal, Mikan, moaning over her lack of a partner for a Christmas date. Mikan tells her little brother Leo (an 18-year-old) to securely take Yuuko home when she slips and damages her ankle. However, as they arrive at her house, Yuuko makes a play on him and they end up sleeping together.
She learns the next morning that not only sleeps with the little brother of her closest mate, she practically gave up his virginity! Leo is not happy with just being a one-night stand, so they continue developing a romantic partnership altogether. Can she hold this from Mikan, and will her relationship grow to something else?