why?

Seeing Dao marks was a potentially supreme ability

But that was in the gu world

Here too it will be plenty helpful

But if it was either the sharingan or seeing the dao marks

He will choose sharingan

Of course, if he could have both it will be much better

The reason he chose sharingan was, growing up as a ninja was not focused very much on dao marks as compared to energy control

And sharingan will give him a higher ability compared to others in the amount of chakra he had and the control he had over it

And of course, even if he lost the ability to see dao marks after fusing the sharingan into his eyes

He was not going to lose it forever, since if he lost the ability, he will store his eyes safely, then fit them back when the need arose

...

He was planning all this, while also taking out the soul from the body of the kid

To do it was pretty simple even with his lacking soul path attainment

He just needed a soul path rank 1 gu and chakra

After taking out the soul, which looked like a transparent infant

He covered it with chakra and slowly brought it into his body, where it started to fuse into his soul

Of course, he will get some impurities in his soul which was previously chaos purified

But he didn't remember that, and even if he did, he wouldn't care much

And as it fused, he received some memories and emotions, mostly longing and love for Uchiha Mai and some simple memories

None of which could impact even in the slightest, his hardened heart

After the soul completely fused with his, the process was complete

And he felt that his soul had risen half a man's rank

He could focus on this path to grow stronger, killing millions of infants

But that would be too much impurities and emotions even for himself

...

After soul fusion, he removed one of his eyes and used utility gus to transplant the sharingan,

It was much harder to do it by himself, but he succeeded in the end since meticulous work and Fang Yuan always complemented each other

In the end, one of his eyes had turned into a dormant sharingan, and looking around, he first tried to see dao marks and as he had expected, failed in doing so

Maybe if he had more attainment in medical ninjutsu, he might be able to fuse both his eye and sharingan together

But that will have to wait

Clearing his mind, he began the transplant on his other eye

This too succeded in the end

Now he had a perfect pair of dormant sharingan,

And he could immediately feel that the chakra source in his body, where everyone's chakra originated from, which created 4 baby fist amount of chakra in his body before

Had atleast doubled in strength

That meant he will have more chakra than ordinary already,

He will have his chakra source and the parasite's chakra source fused into one as his chakra source

No wonder uchiha had more chakra in general than ordinary shinobis

...

Taking out a mirror and looking at it, he saw a dark as abyss pair of eyes looking back at him

This pair of eyes had died once, making it darker and fiercer than others in looks

And the owner of this pair of eyes was the demon himself

...

Now he could truly start his ninja journey

Before that he had to assimilate into konohagakure

The journey has just begun...