Saikin, Imouto no Yousu ga Chotto Okashiinda ga.

High school student Mitsuki Kanzaki finds her life upended when her mother remarries a divorced man with a son named Yuuya. Shortly after the wedding, both parents relocate overseas for work, leaving the two teenagers to live together alone. Feeling abandoned and resentful, Mitsuki keeps her distance from her new stepbrother, refusing to build any meaningful relationship or even hold a basic conversation with him. Her isolated routine shatters when she is visited by Hiyori, a restless spirit unable to pass through the gates of heaven. Hiyori takes control of Mitsuki’s body and begins making bold, romantic advances toward the bewildered Yuuya. To finally reach eternal peace, the ghost equips Mitsuki with a supernatural device known as the TST belt, which charges whenever Yuuya experiences intimate feelings toward her—whether through dates, kisses, or more passionate encounters. Each charge builds a bridge that brings Hiyori closer to the afterlife. Desperate to rid herself of this intrusive spirit, Mitsuki is forced into an impossible dilemma. She must actively seduce her own stepbrother, pushing past her emotional walls and engaging in increasingly daring acts to fill the meter and send Hiyori on her way.