These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Seto No Hanayome
Complete Monster: Yoshio only appears for two episodes, but it doesn't take long for him to achieve Complete Monsterdom when he drugs Sun into a trance and tries to marry her against her will (while planning to do a little bit of This and Thatsoon afterwards.)
Fan Disservice: Sun becoming a man for her role as a lover for Lunar, it's ridiculously manly.
High Octane Nightmare Fuel: The second half of the 2nd OVA, which does a Genre Shift from comedy/action to straight horror, borrowing elements from The Ring. Saturn will probably haunt your nightmares now.
Moe Moe: In one episode, Lunar-papa, Gozaburo, and Masa (ordered to) crossdress as schoolgirls and catgirls and act out moe stereotypes in an attempt to understand a girl's heart. It really is that horrible. Ends with Sun suddenly receiving cat ears, which everyone agrees is incredibly moe (before being blasted away).
Episodes 4,6, and 18 for Mawari, and 12 and 13 for Lunar; Lunar was also technically the first girl to confess her true feelings to Nagasumi as well.
between them was never spoken of ever again after a certain point, and they reverted to how they were before said development. Which is sad really, as that would've made the plot more interesting.