The boyfriend knew how much Japan meant to his girlfriend and yet planned a trip without her, leaving her feeling excluded and unimportant. He has never said he loves her. His actions speak louder than words, and they scream indifference. The boyfriend's behavior suggests a lack of consideration for her feelings and a disregard for their shared dreams.
The girlfriend is overreacting to a simple vacation. The boyfriend is entitled to travel where he pleases, and her disappointment doesn't warrant ending a two-year relationship. The girlfriend is insecure and controlling, expecting her boyfriend to prioritize her desires above his own. He probably just wanted a break from her constant nagging about Japan.
The boyfriend's last-minute trip planning, knowing his girlfriend couldn't join, does indicate a lack of consideration. His behavior in Japan, involving partying and interacting with other women, further exacerbates the situation. However, the girlfriend also bears some responsibility for not communicating her expectations more clearly and for allowing her disappointment to fester without addressing it directly. The lack of expressed love from the boyfriend is a separate, but related, issue that should be addressed in its own right.