this is the type of story that i always wanted...an SI...way way before cannon....but why the low rating?...dude dosnt have SI knowlede, he is just a random person [so yah its a bias review]...author man, could ya give MC SI knowledge?, it would be more interesting...like you could make up a BS reason where he just " suddenly remembers "
suggestion: just the generic ****/.....OP smart MC,,,,,,but hides it...ruthless and cold, not some idiot that shows his power, one man army, no retarded perverted MC, add some romance and fluff, just build it, no shallow ****.....also since its 500 yrs before cannon...maybe make MC a kenpachi?....dude is before uruhara, yorochi, isshin.....
zanpactou ability: yoru....creates a dark domain that is under MC's control...MC has ability to devour other abilities......MC also has wood style, like hashirama, can create forests, 1000 m tall mechs, wood giants and exploding dragons and ****..this could be shikai, the yoru could be bankai.....
MC could use the wood style to go to the the hollow world and create a place for hollows?