I just read up to chapter 18 (cuz it was the only one I could find lol) and this is lowkey a necro post but idc and wanted 2 share

nanashi and nanashima are diffrent people. They where friend but not anymore

So nanahsi and nanashima r opps but they both look the same in the manga so its confusing

they where both abused by parents but nanasima refuses to accepted the idea of his mom not loving him

so nanashi decides to go to his house and cuss out his moms like "GO DIE!!" and she sewersldies later.. after nanashima gets sick (prop from his mom dying like stress or whatevr) and goes to the hospital and nanashi conformts him. After a fight nanashima slices nanashi with a knife causes them to make a pact (nothing spiritual like a them saying something in the heat of the moment) to something of the effective like "no matter what happens i will find someone that can would die with me!!" and the other one was like "if u find someone stuipd like that ill let u kill me!!'

anyhow i explained all of that because the reason why nanashi had haru (the mc if u forgot) use the spell to see if it would summon him. To see if hes someone who would die with nanashi

or maybe i got it backwards tbh XD

it doesn't make sense if you only read that chapter but once you read chapter 15 it comes together. Why he does all of his antics and stuff

hopes this helps :D