A Viking insect is a firefly. In the insect kingdom, the insect most resembling a Viking is undoubtedly the firefly.
The Viking firefly is attacking Hotaru (ほたる) Tomoe (alter ego of Sailor Saturn) because the Viking firefly hates the show Sailor Moon and everyone on it. Hotaru screams in terror as she is deathly afraid of fireflies, especially Viking ones.
Currently there are no similar looking kanji which exist in the WaniKani learning system