Hiro encourages his girlfriend Mizuho to get in shape through swimming, but the tight swimwear leads to erotic encounters both in the pool and at the beach. Simultaneously, Takuya develops an intimate relationship with his clumsy neighbor, Sayaka, after helping her with a household mishap, discovering a shared passion for the thrill of swimsuit-clad romance.
Julie and Hiro enjoy an erotic shopping trip for a provocative white swimsuit, while the timid Shiori undergoes intense sexual "training" from her sister and Hiroto to prepare for her first date. Meanwhile, the ninja Kuu's assassination mission at Wanimaga Castle takes a turn when she is captured by mercenaries and discovers an unexpected, insatiable pleasure in her defeat.
After waking up in Wanimaga Hospital following a bizarre accident, Hiro receives a provocative visit from Mizuho, who uses her newest swimsuit to turn his recovery into a secret sexual encounter. However, as the pair enjoys their risky tryst, a group of mysterious ninjas infiltrates the facility, stalking the halls in search of their targets.
While Shou enjoys a passionate encounter with Suzuka and Marino, a surreal conflict unfolds as the ninja trio Yami, Tsuki, and Kage hunt the elusive Kuu. Through a series of erotic battles and dimensional shifts, Hiro forms a deep bond with Kuu before she vanishes from his world, leaving behind a chaotic and confusing aftermath.