Ima wa Mada "Osananajimi no Imouto" Desu kedo. - Vol. 1 Ch. 3

[MangaDex]

 

[SilentWInd]

For some reason he's acting like this star tear is an powerful relic and he's a stoic guardian trying to protect the world from people abusing its power. Even though its probably just a rock and this is just a childhood trauma hes overreacting to.