If you're a titles chasing degen like me, know that this one is a b to get. You're looking at in average one Gehaku spawn per two hours of grind so plan for between 50 to 60 hours for this title.

According to my data Gehaku spawns about 5% of the time after you've triggered the mob rush mechanic (the world weary soul thing) and defeated the giant fighter. I'd need more hours to confirm these numbers but it's definitely between 5 to 10% in any case.

the trick to get as many of the spawn events per hour as possible is to never spawn more than one world weary soul at a time, for this you're gonna have to figure out what mob groups can make one spawn (they don't seem to spawn for all mob groups) and then make your rot only involve one mob group that can spawn the soul (you're probably looking at a three or four mob groups rot then. If you spawn more than one by making your rot bigger, the souls will go to either world weary soul and when you split them like this you risk not being able to spawn a soul'S complete mob rush before it despawns resulting in a lot of time wasted,.

Also once the world weary soul has that purple circle around it meaning it will spawn mobs if you get within the circle, don't go yet. Kill mobs around it and wait until it has gathered at least 5 more souls, then once you trigger the mob rush it will be a complete one. If it doesn't have enough souls it only will do maybe half of the mob rush and then you'll have to get it to gather more souls after and that will take much longer than if you'd just waited to feed it five more souls before triggering it. with that method you might be able to finish up to 8 complete mob rush per hour. That's 8 chances at Gehaku per hour then. Which why you should probably do at least two hours a day because else you'll be there for two months instead of one.

In any case, may the rng gods favor you.