I was doing some runs of the game's hard mode and I figured out it was faster to enter hard mode through the time trials rather than the normal entrance. After completing the game through the time trials, a different end cutscene played and it transported me to a special secret world.

Is this world intended to be part of the Hard Mode speedrun?

If it isn't intended to be part of the speedrun, I would propose an any% and a 100% Hard mode speedrun. You would only have to beat the secret world in the 100% run.

I now have screenshots of the Secret World.

https://steamcommunity.com/profiles/76561198199224154/screenshots/?appid=502130

I plan to upload a video of a playthrough of it tonight.

This game has multiple endings based on which mode you played. Finishing hard mode with less than 20 deaths or finishing time trials mode within certain amount of time, will give you different ending.

If the time trials becomes the main way to speedrun hard mode, I think getting to that secret ending should be included, since that would be faster than having to wait few minutes just to skip that secret ending.

Here is the video of me beating hard mode:

Is there another ending that you know of other than the normal one and this one?

I believe secret ending for hard mode/hard time trials mode is different. i don't know there's more