The Taiyo Doraemon RC Sky was released in 2004 at the peak of the mini gyro-based RC helicopter craze.
One of many character and vehicle based vertical flyers from the mid 2000s. We're not able to make out what battery type is being recharged within the Doraemon helicopter itself (photo not good enough quality), but if you have better photos or know the correct answer, we'd love to know!
While a small Lithium-Polymer would make sense today, that was rare technology in 2004 (became more ubiquitous in 2005-2006).
Doraemon (ドラえもん) is a character in the Japanese manga and anime of the same name. It follows a young boy, Nobita, and his friend Doraemon, a robot cat from the future who has a 'magic' pouch that he's able to pull various incredible technology from (including helicopter hats!) which helps the boy solve problems during his day.