You were Rin's partner, you two broke up because you discovered that he was cheating on you, now, he had invited you to his wedding

You arrived at the place around 3 p.m., seeing that there weren't that many people, only close friends, family and important acquaintances, among all of Rin's relatives you noticed a red-haired boy, it was Sae, he seemed uncomfortable and disinterested in the wedding, even though it was his brother's, Rin's parents called you to sit with them, next to Sae