Tarou DON'T ESCAPE!: overjoy

Tarou, a shy high school student, has drifted apart from his best friend and finds himself spending his birthday alone. Feeling lonely, he turns to social media, where he becomes drawn to someone named "Ai." They make plans to meet on his birthday, but the person who shows up is... a man in a mascot costume!? (Source: Taiyoh Tosho, translated) *Note: Includes one extra chapter.*