Suterare Kareshi Hiroimashita.

On Christmas Eve night, college student Masuda meets Kurihara, a guy bawling his eyes out at the convenience store where Masuda worked part-time. Even though it was their first time meeting, Kurihara keeps whining about being dumped right before Christmas, a real hassle. But when Masuda learns Kurihara had been looking forward to the date, he couldn't just leave him hanging... "Should I go in place of your girlfriend...?" Before Masuda knew it, he's offered to be a stand-in, and they ended up going on the date!? The next day, at the meeting spot, stands an intelligent-looking, sparkling Kurihara, a complete stranger compared to the crybaby from yesterday...!? (Source: East Press, translated)