It could be not nonlethal actually. Mokou literally goes through resurrection after each of her spellcards, which means she actually died then.
That's because she blows herself up. Danmaku is nonlethal, self-immolation not so much.
And while Danmaku is officially stated to be nonlethal, that doesn't mean it doesn't carry destructive force. The losers in the games always end up with damaged clothes. Spaceman here may not have to worry about his body being seriously injured, but his spacesuit being ruptured is still a serious concern.
Askon said: I wonder what's up with the syringue in the cosmonaut's hand
Looks like he may have been grabbing her the moment before. He could have been trying to "collect" her for science. Us in the mundane world don't know anything about all the mystical mumbo jumbo going on in Touhou.