I made a simple auto-splitter that starts the timer on new game and splits on entering the overworld map. So it splits when finishing a level, but be aware that exiting a level prematurely also causes it to split.

It splits a second or two before the screen completely fades to black, so it's a bit different from what we were splitting on before.

For the ending I manually added 5.0 seconds from when Odokuro (final boss) gets the final hit to line up with when the screen fades to white. A bit jank, but seems to work fine in practice.

(You can get the autosplitter via LiveSplit's Splits Editor window)