Netsuai Prince follows Amamiya Matsuri, whose life takes an unexpected turn after her mother's remarriage. She finds herself the younger stepsister to Haruka, Azusa, and Rihito, the famous triplets from the popular group Terzetto. Matsuri, who always dreamed of having close brothers, is disheartened to discover the siblings are constantly at odds. When she learns Azusa secretly longs for family unity, Matsuri dedicates herself to bringing them together.
A welcome party planned in her honor quickly reveals their deep-seated conflicts as the brothers clash during preparations. However, a sudden health scare when Matsuri collapses forces the worried triplets to call a truce. Determined to create a harmonious family, Matsuri continues to intervene in their arguments. As family bonds slowly begin to mend, Matsuri receives a surprising confession of love from Azusa, adding a complex romantic layer to her mission of uniting her new family.
Other names: Netsuai Purinsu, Netsuai Prince: Onii-chan wa Kimi ga Suki, ねつあいプリンスおにいちゃんはキミがすき, 熱愛プリンス お兄ちゃんはキミが好き, Secret Love with Prince