How to extract the main vocal from the secondary vocal?

[dry wyvern]

For example, this song: https://www.youtube.com/watch?v=5zLrpMYB8uo
The female voice is the main vocal, however, the male voice which is the secondary vocal also appears at certain intervals, and I have to say, it really badly affected the quality of some of my works. I was planning to let Yukari Akiyama sing the song, the parts with only the female voice were of high quality, however, the parts in which the secondary male voice sang along with the main female voice were of terrible quality likely because of vocal dilution, so I figured the solution is to extract the female main vocal from the male secondary vocal, but I don't know how.

Here's my result in case you're wondering:

[green zenith]

Use a vocal extraction app =3

https://aihubdocs.github.io/en/ check the vocal isolation page to learn

[unique forge]

Use BV model in UVR

Or BVE V2 model in X Minus (it's paid but i recommend it since its works well for me)

[dry wyvern]

I didn't even manage to reach the extract lead vocals process because of this error

[dry wyvern]

What do I do now?

[surreal osprey]

Ayo? @dry wyvern level 1 !!!

[unique forge]

That's a pretty weird error, it never happened to me.