Good Poppoya clone - the tennushi is a veteran of Poppoya in Yushima. The place is in an area of Nakano near Nakano Broadway known as ふれあいロード or Fureai Road. Probably 5-10 other ramen shops within 3 mins walking distance from here including a branch of Aoba. All sorts of other interesting shops around here too, this place is probably worth a couple hours of exploring time. Very simple menu - ramen, tsukemen or abura men. Very oniony and garlicky and salty broth. Various free toppings as you can see on the pictures on the link below. Not clear here whether Kaeru means "come back/go back" or "frog" as there are no kanji that I can see.