This is easily done with the shotgun in the "Old House". After meeting Marguerite, instead of trying to avoid her, attack her. She will send a swarm of small insects after you. Shoot the swarm and you should kill way more than two of them with one shot.
Here is a video guide with English commentary!
Here is a playlist of guides for this game!
https://www.youtube.com/playlist?list=PL-HeW6XkKdUKUtj7CV_kW...