NileGuide Expert tip:
Ask for "kata-men" (hard noodles) and save some of the soup for a "kaedama" (extra noodle serving).
Maru-kin (丸金) has locations all over Tokyo, bringing standard "Hakata tonkotsu" - Fukuoka-style ramen made from pork bones - to eager locals. Although the bowls are smaller here than at other ramen places, it's because of the incredible richness of the soup produced by boiling pork bones for days. Hold on to your soup and finish the noodles first, then ask for a "kaedama" (extra helping of noodles) for the genuine experience.