Taste over tradition
A late night gorge at a typical Japanese junk food restaurant just can't be beat. One thing which I always go for is ramen, but not just any ramen. Taste over tradition is the key concept, and many older or more traditional Japanese people scoff at some of the wild creations that downtown ramen shops come up with. One of my personal favorites that I recently had is apparently originally an Akita prefecture creation: Miso Curry Butter ramen!
Heavy and deep flavor with just the right amount of buttery roundness to balance out the salty combination of curry and miso. I had this ramen in Roppongi at a place called "Roppongi Ramen (easily enough)". This place is near the station and a great option for on your way back.