About the tattoos: 1) on the neck and shoulder, in French "Vivre sans regrets", it means "live without regrets"; 2) on the back, in Latin, "Ab imo pectore", it means "from the bottom of my heart"
Seojin acts like she's a dog in heat, even though she's in love with Sera and wants to be her girlfriend, but she doesn't stop trying to have sex with everyone.
The manga has an interesting proposal, it's just a shame that it was very rushed and a bit confusing. But it's really funny and worth reading.