In '虜ノ旋律 -refrain-', Binkanoppai presents a taboo tale of forbidden desire. Teacher Aina Remine finds herself in a classroom of eager, busty students, their lustful gazes fixed on her. As she attempts to teach, their large breasts heave with anticipation, drawing her in. She can't resist the temptation, surrendering to their advances. One student's massive tits spill out, Aina eagerly taking a nipple into her mouth. Another, Remine, spreads her legs, inviting Aina's fingers to dance inside her. The classroom echoes with moans as Aina's lesson plan evolves into a symphony of flesh, culminating in a chorus of creamy finales.