Slug Girl, or Melk as a companion, is a monster in Monster Girl Quest: Paradox
“With her body that of a soft slug, weak attacks will get stuck in her mucus covered membrane. The Slug Girl's behavior is to take walks at night and attack any men she encounters. Like most monsters, her staple food is male semen. Using the lower half of her body, she carefully stimulates her catch to feed.
Once she catches a male in her slimy mucus membrane, they are forced to ejaculate with surprising ease. With that, she is able to feed.
In addition, if the Slug Girl particularly likes her catch, she will use the genitals in the slug half of her body to mate with her prey. Using the same techniques as feeding, she will force the male to release just enough semen for copulation.
Once a suitable male has been found to copulate with, the Slug Girl will continue to use him as both a mate and a source of food for the rest of his life.”
- Slime Attack-Normal Attack, One Enemy, Slime 50%
- Poison Attack-Normal Attack, One Enemy, Poison 25%
- Sticky Slime-Pleasure Attack, One Enemy, Slime 75%
- Slimy Caress-Pleasure Attack, One Enemy, Slime 75%
- Climb Over-Pleasure Attack with Bind, Target:Luka, Slime 75%,
- Slug Crush-Rape, Slime 75%
Since your equipment is still likely to be limited in this part of the game, there isn't much you can do. You should have Sonya in your group, who can use White Magic to heal you and use club skills especially deadly to slime creatures, like Slug Girl. Lime can also help here if you recruited her. She can steal items from them which can be surprisingly useful. If nothing else, she's another party member to deal damage with.
The fish boomerang can still be helpful here, so if they appear in a group, using it isn't a bad idea. But switch back to the custom sword when there's only one of them left.
"So you've come here after being defeated by a mere slug... This adventure is going to be so very painful. Slug Girls will try to slime you. When you are slimed, you will take heavy damage from pleasure attacks. However, defeating your enemies should be faster than treating this ailment, assuming you even can treat it at this point. If you're bound while slimed, you will have a very rough time. Have your party members attack that monster to free yourself immediately. Slimy, sticky monsters are very conductive, and therefore weak to lightning, but it's probably faster simply attack if your level is high. Now go, oh brave Luka. Make sure you don't lose to weak monsters such as these again."