How his power would work

Each time he sleeps that will be his check point like a bonfire.

He will gain souls and human effigy through slaying ninjas.

Souls will be gain through each ninja

Every human will have an effigy even a civilian

Genin - 100 or 500

Chūnin - 1,000 or 5,000

Special Jōnin (basically a half Jōnin) - 10,000 - 15,000

Jōnin - 150,000 - 200,000

Anbu - 350,000 - 500,000 (forgot to add this)

Kage - 1million to 5million

I might change this, depending on how many disagree on this ranking

I'm not sure how he will level up, I haven't decided on through resting like dark soul 1 or through a hand maiden like dark soul 2 or 3

He might get a merchant that will sell all the weapons, armor and spells from darksoul 1 to dark soul 3 - I might change this where he could gain armor, spells, weapons from ninjas but I'm not sure how people will like that.

Str - the strength to wield large and heavy weapons. Maybe even lift a tail beast up like nothing once reaching the max.

Dex - Dexterity to use complex weapons like rapiers or two wielding curve swords. also how fast his able to swing his weapon. P.s this also helps in casting spells and when he falls.

Vigor - Increases regeneration of wounds and cut of limbs

Vitality - How hard his bare skin able to resist attacks, also increases resistant to poison. The higher Vitality is the more his body can bare, like heavy armors and rings.

Attunement - how many spells he can remember at that time, and how big his mana pool is.

Endurance - how fast he can run, also increase lighting and bleed due to his muscle being compressed and flexible.

intelligence - his ability to learn spells faster, also to use pyromancies and the needs to use that spell. increases ability to break from a genjutsu

Faith - basically his will also the ability to use miracle and pyromancies, increases his resistant to genjustu. (I think you need lot of will be resistance to genjustu because it doesnt matter how smart you are, this is proven due to kabuto unable to break itach genjustu until way later, because he accepted who he was, that requires will not intelligence.)

Luck - I don't know how this will work because in dark soul it increases the ability to discover items on enemy bodies, so maybe ninja will have more ryō and items?

Also, luck will increase how fast the main character will be able to apply poison. it also increases resistant to curses. (so take that orochimaru)

Five stages of hollow

first stage - his body is decayed at a minimum; his body will smell as rotten flesh. only some part will show has decaying like a rash. Won't affect him in any way

Second stage - Some decaying will appear around his arms and legs. he might feel tired and has harder time remembering old memory's

Third stage - his body feels weaker, his face will now decay, and his hair will start falling off. he will have harder time trying to use strength or use any type of dexterity.

Fourth stage - will have a hard time focusing, will become dull at random time, his hair has completely fallen off. his whole body is decaying, his at his weakest form.

Fifth Stage - Madding stage, he became a hollow, will attack everyone even allies. he's much stronger than his human form. he will attack humans on sight until he has a human effigy through a ninja or a civilian.

Human effigy will reset his hollow form.