@Plippity bet that he goes to Osaka. He doesn't want to visit the event, but girl visits his parents, making him nervous. His parents like her.
She gives him a ticket; his parents oc react and pressures him to go, thinking its a date. He decides to go. In the end, he hurts her feelings, and he runs away. She runs after him and confesses.
At first he was so positive, thinking he could go out with her. Now presented with the chance, he wavers. Why you may ask? Because she manipulated and toyed around with his feelings, making him uncomfortable with dating the idol.