Chocoholic by Swimmer is a great cake/sweets and gifts store located within Ikebukuro Station. They have really well decorated cakes that are delicious and are very inexpensive around $6AUD. More details can be found here
If you purchase a cake or something that is refrigerated the staff will ask you how long it will take you to get home/to your hotel and they will put these ice packs on the box free of charge. Another great example of fantastic Japanese service.
This Neko shaped cake is Milk Tea flavoured and is delicious.
TaylorとTokyo 