I want to try speedruning this game, but I can't find any guides. Can someone give me a few tips or link a guide?

There's very little randomness to the game, so speedrunning is more like a checklist. If you just take the exact same actions I did in the posted videos, they'll work every time.

As far as the stat assignment and non-random parts of the secret ending speedrun go:

Restarting at prologue: Max out Earth and Fire, put remainder into Water.

1st labyrinth random encounters - Use Power Strike against the rat with grenade or blue rat. Use Swift Strike against the rat pack.

Fire Salamanders fight - Always start with 1 Power Strike.

Then, depending on what the Salamander uses, make the following replies: Burning Breath ► Power Strike Power Strike ► Flowing strike, Swift Strike Fireflash ► Brace, Flowing Strike Bite ► Flowing Strike Swift Strike ► Power Strike

Great lesson labyrinth - part 1:

1. Right
2. Back
3. Left
4. Left
5. Back
6. Straight
7. Right
8. Back
9. Straight
10. Left
11. Back
12. Right
13. Back
14. Back
15. Back
16. Right
17. Left
18. Left
19. Back
20. Right (looks like a pit)
21. Left
22. Back
23. Right

Great lesson labyrinth - part 2: From Start: Straight, right (answer to square root math question is 51) From Infinity: Left Left Right (do lesson) Left Right Right Left (do lesson) Right Right Left Left (do lesson) From Faith: Right Left

Compassion Ending stat assignment - 50 Fire, max out Water.

Survival Ending stat assignment - Max out Fire and Earth.

Final restart stat assignment - Start out on Earth and go clockwise, adding points up to the next milestone. Once almost out of points to assign, -1 Fire, +1 Water, remainder into Air.

Allmother's trial encounters - Flowing Strike against caterpillar, Power Strike against everything else.

Fighting Tempest & Vantage - Just use Power Strike.