I know exactly the place and the very stairway they most favored --nearly got my a$s kicked there for taking photos of them cuz it was so incredible.
It was the steep one above the station in the park that comes down near
AmeYoko-cho. It was totally out of control, I'm so happy they got ahold of it.
Equally amazing is the way they've been able to scrub their history about that so well.
Ikebukuro station and the surrounding areas were really getting whacked, too. Lots of burglaries and rapes. Maybe the Yakuza were keeping them out of Shinjuku but the east side of the JR line was downright dangerous.