I've noticed that little suction marks or tiny punctures pop up in anime more often than you'd expect, and I think it's a mix of symbolism, shorthand, and a love for romanticized tropes. On one level, those 'sweet bite marks' are just visual shorthand: a quick, readable sign that two characters have been physically intimate, that someone left a mark as proof. In Japanese media you'll see 'キスマーク' (kiss mark) or sometimes literal vampire punctures in shows like 'Vampire Knight' or the darker bits of 'Monogatari', and the audience instantly understands the relationship change without a long exposition.
Beyond convenience, there's a strong emotional and thematic layer. A bite can imply ownership, jealousy, or protection — it dramatizes affection in a way that’s simultaneously tender and a little possessive. That ambiguity is delicious for storytelling because it reinforces character dynamics: the clingy type, the dominant protector, the obsessive lover. Creators can play with consent and power subtly (sometimes problematically), and viewers decode a lot from how the marks are placed, how other characters react, and whether the bitten character is embarrassed or proud.
Finally, there's the fanservice and fetish side. Sweet bite marks are visually evocative and can be used to hint at more adult content where explicit depictions would be inappropriate or censored. It's an aesthetic choice as much as a narrative one — cute, sexy, or eerie depending on the tone. Personally, I find it fascinating how one tiny mark can carry so many meanings; it’s a small detail that says a lot about the characters and the mood.