Where to go from Kumamoto/Fukuoka? First time in Japan.

Hi all,

Question: I have a work trip to Kumamoto from 8-12 November. I am planning to solo travel for about a week after (13-19). I was wondering what the best option would be and how I should split my time?

Tentative Ideas: I will probably spend some time in Fukuoa because it's close, after that I'm not sure whether to explore the Kyushuu area, or fly to another major city e.g. Osaka/Kyoto/Tokyo to spend a few days. I imagine the former option might make more sense/be cheaper but because I've never actually been to Japan before I can't help but feel a bit FOMO to spend all my time in a 'side' area.

My preferences: I love seafood, I like the weird gimmicky stuff I see on social media (e.g. pokemon, anime, capybaras), history and am also planning to do a tiny bit of shopping. I am more budget conscious as I've only recently entered the workforce.

Thanks all for any advice!