Can someone please tell me in which season chuuya n dazai got married??😅

Hi!! I'm new to the bsd fandom,I just joined last week actually😅 and I've been obsessed with bsd since!! I've only watched till season 3 and also some tiktoks,I wanted know in which season or manga chap did chuuya and dazai get married?? It's my first time watching a bl anime so I am bit clueless on this.I usually read manhuas so could anyone help me:3