After breaking up with his girlfriend, Natsuno is homeless and spending nights in his office. At a mutual acquaintance's wedding celebration he meets up with his old school friend Ui, who had confessed to Natsuno just before graduation, been rejected by him, and drifted out of contact. Now an accident has left Ui with amnesia, and his first words to Natsuno are "Who are you?" Hoping to charm the other man into lending him a place to crash for a while, Natsuno lies, "I'm your ex"...!?

(Source: MU)