Marmot is found at the end of the Hotel located to the left of the Apartments floor shop (Level 3-4). After first encountering Marmot, you can fight him again at the laptop in the Refuge (starting area). If unlocked, use the Pride modifier (found randomly in dark grey boxes in shop areas) and avoid getting hit to guarantee an M rank upon victory. Otherwise you can increase rank via "stylish" moves such as aerial kills, dodging, parrying, and dealing damage without getting hit.