Nisekoi Doumei.

A girl and a boy pretend to be a couple as part of an arrangement, engaging in a secret act they describe as a "crime." After witnessing their respective partners betray them, the two begin their partnership as a form of imitation. Their relationship is described as both sweet and painful, with the girl experiencing conflicting emotions between the deception and her genuine feelings. The story explores the development of their bond amid the fabricated relationship.