True he can hide the knife in his pocket so he can take it out more faster.
This story is really slow burn. And sadly, there is no much romance or exciting moments in it.
I just love the draw style and the hardwork the author spend to build this story. But I just want to know the whole meaning of them remember their past life for as soon as possible.
So if you read a bit between the lines, it's all a plot from the spirits. The whole meaning is here but you have to piece things together a bit.
The Spirit is basically a parasite. It's turned into a mythological story in Veronica's world : "it took pity over the dead people killed by magic and reincarnated them", but the real truth is that it uses "death by magic" to spread over new people, so to speak. Or if you put it another way, it's the Devil's whisper. "I grant you power, use it as you wish" and when humans use it for conflic, bam, new hosts.
Minami mentioned it before, but even assuming everyone behave now, there is no guarantee they all will later in their life. Right now they can mostly keep magic under control and avoid as much as possible to showcase it or affect ordinary people. The only outside victim until now is Minami's friend, and somewhat their teacher who is suspicious of them.
But life is long, and shit happens. What if someone else use magic and hurt, or even kill someone else ? What if the forbidden spell is unleashed once again, this time on the massive population of Japan ? Well, what will happens is all these people will reincarnate, either in this world's or in another. This time, most probably with magic as well. In the blink of an eye, the world would be under the spirit's influence same as Veronica's.
The Church is basically how the spirit control everyone else btw. It's not even destructible from the inside, as Nishina/Lucas discovered: if your goal is the destroy the Church, the very second you get access to the highest rank and get "the honor" of being possessed for the first time, you are forced to speak your inner thoughts, so if you blurt out "I want to destroy the Church" you immediately get purged. It's a failproof system.
The only chance Minami and the others have, right now, is to get rid of the Spirits inhabiting Nishina and remove them from the world completely. Or else they'll become a ticking time bomb for pretty much the entire world. Their main advantage however is that the Spirit is not human, it's a lot more alien and very naive/shallow in its comprehension of humanity, so they can act and deceive it while the spirit is spying on them, hence the clown show Nishina, Zeze and everyone else is doing.