[Sangetsu]

Kabukicho isn't so dangerous, I actually think it is more interesting at night than during the day. You'll see the usual groups of hosts hawking to young women, and the occasional hustler doing thr same to men. You might get approached by one or more hustler if you are in Kabukicho, but no one will attack you or rob you. The area around west gate park in Ikebukuro is similar, and maybe a bit riskier.

In the rest of Tokyo, don't be afraid to explore the smaller streets and alleyways, you often find interesting things there. Nowadays I usually avoid the touristy areas if I can, there are many intersting places where tourists don't go.