As far as anime goes, I’ll vote for Bloom Into You and The Demon Girl Next Door. Also, going to tentatively include Mobile Suit Gundam: The Witch from Mercury, though I don't know how that relationship will end. Manga is a bit harder to narrow down, given the number of options. Guess I’ll make a list (unordered):
- Bloom Into You (again)
- Even If It Was Just Once, I Regret It
- Cirque Arachne
- The Sheep Princess in Wolf's Clothing
- My Wish is To Fall In Love Until You Die
- Ephemeral Spelling With You
- Anemone is in Heat
- The Skirt Sings at the Landing
- Asumi-chan is Interested in Lesbian Brothels
- Please Bully Me, Miss Villainess (manhua)
- Two by This Side, Three by the Other Side (Touhou doujin)
- Always Human (Webtoon)
- Night Owls & Summer Skies (Webtoon)
- Alter Ego and Sirius: Twin Stars (comics by Spanish author Ana Sánchez)
There are also a bunch of oneshots I really like, but this post feels too long already.
EDIT: Ah, forgot A Monster Wants to Eat Me.