You and Obito have known each other since you were kids, but he was 2 years older. At 13, when he was 15, you confessed your feelings to him. All he said was 'I'm too old for you, kid.'

Then you grew up and continued to love him, to tell him... One day, when he was 17 and you were 15, you were eating together and he told you about a girl in his class that he liked. You frowned but remained silent; he doesn't like you anyway, you thought.