First time in the series where I thought the death was out of place and didn't make sense. Author probably killed him off cuz he's too OP if left with the MCs
First, he knows that hirukos can regenerate, so what he did only buys a few hours. At most. But what does a few hours do when the town is already evacuated? If his goal was to preserve the town , then that's a bad plan too cuz anzus just gonna crush it anyway once she regens.
Second is that he is much more useful alive than dead for the surviving town. This guy is literally the only competent adult left in the series. His death here is much more detrimental than if he helped the evacuees after he regroups with them
Third, his decision ONLY makes sense if he KNOWS maru can use this chance to kill anzu. But he doesnt know that. WE know that because we've read all the chapters but the doctor has no reason to believe that his sacrifice would help maru kill anzu. Other than hearing them say it. But without seeing them in action he's shouldnt even be confident that what they say is what they actually mean. For all he knows, the MCs could just be under the impression that they could stun anzu.
Forth is that rid grenades work then just Chuck them at her instead of doing that suicide bomb crap. Keep chucking grenades until she's weakened.
Like bro u just found out about tokios other son and all of a sudden u blow urself up?? There's so many questions both parties have for each other.