It won't be challenging at all. Lots of amazing Japanese food that doesn't come from the sea - Ramen (noodles, normally in pork and/or chicken broths, and usually topped with pork), Beef rice bowl, yakitori (grilled meat skewers, primarily chicken and pork), yakiniku and shabu shabu (grilled and steamboat respectively, primarily beef), tonkatsu (breaded deep fried pork cutlet on rice), etc etc ...

... unless you have seafood allergies. That might be a bit tricky.