BG Music: World End Dominator, by zts, from Umineko no NAku koro ni. ♥ Ryuukishi07
Here's a run of Half Minute Hero, Hero 300 Normal Mode in 03:40"50.
I definitely made a good deal of visible mistakes here due to still having some unfamiliarity and lack of reflex with the stage's layout (standing in random spots for no reason, running into stuff and stopping; this is especially prevalent near the end as I waste a full second stopping in a couple of spots on my way back to kill Super Noire), this is more for a reference for others should they find it useful, and I am sure this time can be beaten with some more practice (or already has been, for all I know).
The most important part of this run I think is intentionally dying after getting the Trident to save the time it takes to make the trip back to the castle; upwards of 20 seconds, depending on how lucky you get with managing to get yourself killed after getting a weapon that pretty much demolishes everything in that area.