The Pokemon Center in Ikebukuro is the original Pokemon Center Mega Tokyo and currently the largest one in Japan. It’s located inside Sunshine City, and the mascot for this store is Pikachu riding a Charizard Y. Each Pokemon Center has their own exclusive item(s) which can only be purchased at that specific Pokemon Center.
All things Pokemon! Toys, accessories, treats, snacks, sweets, supplies, you name it, it’s all branded Pokemon. The store carries all starter Pokemons from the past and present. I recommend visiting a Pokemon Center if you’re planning on buying stuff for yourself or as a souvenir. It’s much cheaper than souvenir shops. There are also arcade machines like Pokken Tournament which you can play in a separate room.
Some items rotate seasonally, because when I went there I could not find a Rowlet. The only thing I wanted to buy in the entire store and it was not available! >_<