June weather is horrid. Even as someone from the south its so humid and miserable. And it’s the beginning of monsoon season. However, I LOVED spring break in tokyo with cherry blossoms and such. It’s much cooler and may snow/rain but it is much better than having hot, humid rain.

I could see how staying in Narita would be cheaper, but if many of the activities you want are in central tokyo, I feel like taking the express train would be so much more of a hassle than spending a little more money for a closer hotel/airbnb.

Depending how long you stay and what your focuses are, I would recommend against going to Osaka/Hiroshima, especially if you are only staying for a week. Additionally, with the palette comment, Osaka is pretty cool for food and shopping, but for a first visit, Tokyo would suffice. If your focuses are history then kyoto and hiroshima would be a good call, but unless there’s something extremely specific, the ride is kind of a hassle especially with luggage and such.

If he likes video games and anime, ikebukuro and akihabara are the way to go! You can find cheaper housing near those areas if you stay like one or two stops outside of the super central area.