16-sai, Shinkon Hajimemashita.

A girl named Wakaba, who was promised marriage by Sou-chan at age six, faces uncertainty as she approaches sixteen. Sou-chan's memory of the promise and Wakaba's honesty about her feelings become central as financial troubles arise from Sou-chan's father's failing business. Meanwhile, Matsutani Mika struggles to keep her late father's pastry shop afloat with no customers, seeking help from Katsuya. In another storyline, the idol group 'Infinity three' and their manager face a crisis after a scandal emerges, threatening their unity. Additionally, Ichika, who enjoys creating Vocalo songs but is too shy to share them, discovers popular classmate Iori-kun listening and crying to her music in the classroom.