What to read after I Saved Too Many Girls and Caused the Apocalypse: Volume 4?

Rekka may think he's learned a valuable lesson about friendship and the people he loves, but putting it into practice wasn't supposed to be the hard part! When Iris, Satsuki, and Harissa all ask him for a date on Sunday, it will put his wits to the test. But if he thinks his worst dilemma is figuring out which girl to spend his weekend with, he's got another thing coming--more heroines! A new transfer student appears to have a mysterious connection to him, but someone--or something--is after her. And a strange phone call from Hibiki...leads to a treasure hunt?