Ah, the wonderful time killing pastime of a pointless semantic debate
Comics as a term to describe the things your shop sells of course derives from their origins as humourous strips in newspapers, 'the funny pages', that sometimes came as a separate insert in the paper, which then developed into non-humourous story telling, longer strips that eventually filled whole comic with ongoing stories, before eventually people started writing long form graphic novels (you can start another argument over what counts as the first graphic novel: Joseph Franz von Goez’s Leonardo and Blandine (1783), Rodolphe Töpffer's The Adventures of Obadiah Oldbuck (1849), Will Eisner’s A Contract with God, and Other Tenement Stories (1978)?)
The term comic therefore isn't specific to a rigid format. If
My Favorite Thing Is Monsters doesn't count as a comic, what about Alan Moore & Bill Sienkiewicz’s Brought To Light?
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They're not the traditional comics format with speech bubbles (there are a few speech bubbles in MFTIM), but they're just a further development of the form.
In Japan there's a distinction between manga (with talking in speech bubbles) and emonogatari (with pictures illustrating the written narrative), for example Miyazaki's Shura's Journey:
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But we don't really have that linguistic distinction in English.
Anyway, tldr: it's all comics