Mako-chan Kaihatsu Nikki – Episode 1 (EN)

In this premiere episode of the OVA adaptation, high schooler Himemiya Makoto receives a long-awaited love confession from her childhood friend, Kaoru. Overjoyed, she impulsively pulls him into a deep, passionate kiss right in front of her house—their very first. Makoto, a busty and energetic tomboy, has always struggled with her powerful sex drive and fascination with erotic things. Instead of repressing it, she regularly indulges in watching adult videos and masturbating to release her pent-up desires. That night, still buzzing from the confession, she retreats to her room for intense self-pleasure. Unbeknownst to her, her perceptive stepbrother has been aware of her secret habits all along. He confronts her with the line, "I know exactly what kind of woman you are," revealing his insight into her true nature. As he begins to exploit this knowledge, the episode builds toward taboo tension and the start of Makoto's "development" under his influence, blending excitement from her new romance with the thrill of forbidden corruption. This sets the stage for escalating NTR-themed encounters in the series.