The story takes place after the TV drama series Ossan's Love (2018). It's been a year since Haruta and Maki pledged their undying love. Haruta has now come back and receives a warm welcome from familiar faces, his boss Musashi Kurosawa and other colleagues. Justice Yamada, a recruit who has been recently assigned to this branch, welcomes him too. One day, completely out of the blue, the headquarter-based project team "Genius 7" shows up at the Second Sales Branch. Project leader Jin Mamiana orders the Sales team to support them in their big project. Maki, who had been transferred and works now at the head office, is among the project team members with Mamiana. Haruta and Maki grow apart, and Haruta teams up with Justice. Then Kurosawa gets involved in an accident and loses his memory, but the loss of his memory is selective and he has forgotten only Haruta. However, when Kurosawa sees Haruta, he falls in love again.. Hilarious and heartwarming, the final battle of Ossan's Love begins.