This is a tool-assisted speedrun. Definitely the most action based part of the Castlevania world. Ultra fast fights which look like being out of a ninja game and very nice glitches and bugs have been used to make this time possible.
From Wikipedia:
Castlevania: Harmony of Dissonance, known in Japan as , is an action-adventure game developed and published by Konami for the Game Boy Advance. Learn about Castlevania: Harmony of Dissonance