After a one-night stand with a charismatic coworker, Rio is taken by surprise when he suddenly proposes! All after being let down by her boyfriend after he forgot their birthday promise. Of course, once a man gets what he wants, he often stops caring. Feeling down, Rio is uplifted when her coworker Miyamoto steps in. Despite being charming and charismatic, he tells her, "I would never make you sad. If you were my girlfriend, I'd take responsibility." Inspired by his conviction, Rio challenges him: "Prove it to me." With a sweet and passionate love that can melt hearts, will his straightforwardness help her rediscover happiness?