[Hikoma Hiroyuki] Onii no Kuse ni after (Seichouchuu no Masegaki ni Ai no Shisshin Acme Shidou) [Hennojin]

Mai, a charming step-sister with a cheeky personality, finds her casual summer plans at the beach taken to an unexpected level. What starts as a simple discussion about swimsuits quickly shifts when her classmates realize just how much fun she is actually looking for. As the tension rises under the sun, the boundary between a family relationship and a daring public display begins to blur, leading to a provocative encounter where Mai's playful attitude meets a much more intense reality.