You decide that this Monster Girl probably has something to do with the others given how she talked, so you've decided to defeat her to teach her a lesson!
As you rush towards her backside you're shocked that your head only just clears her butt! You stab into her butt with your wooden sword and you're shocked as you can't seem to pull your sword out! "O-oh! Is someone there?" the woman questions as she grabs you with her hand, bringing you up to her face. "Oh! Hello there! I never thought a human would want to visit me!" She said with a warm smile as her other hand went to her rear and pulled the sword out. She eyed the weapon and to your surprise, tossed it in her mouth and chewed it up! "You even brought me a snack! You're so nice! My name is Mary." This earth elemental sounded very airheaded to you, as she completely missed the fact that you were attacking her, not bringing her food. You struggled to get out of her grip, but she had a tight grasp on you.
"I'm so lucky that I found you! I've been begging for a man for a long time, but I was never fast enough to catch one." Mary said with the same warm smile as she began to tug at your pants, pulling them off and tossing them into her basket, she opened her hand as she brought you closer to her face. Out of instinct, you attempted to jump off her hand, but found that you were glued to it thanks to her slimelike nature. Even though she was made out of a mud, her dirt skin actually felt like regular skin. "No running away! Now that I got you, I'm never letting you go!" Mary said as she brought you to her mouth and began to lick at your crotch. To your surprise, her tongue left very little residue. Only a few traces of dirt were left on you as she continued to lick at your crotch, resulting in you getting hard. "You're perfect! I can't wait to try you out..." Mary said as she used her finger to play with your now erect penis. "Please stop! I need to get to the mining town!" you pleaded as Mary giggled a bit. "You're not going anywhere now! I caught you fair and square, and now you're going to be my husband!" You began squirming hard, this isn't how it was supposed to go! If you couldn't even get away from this Earth Elemental, how were you going to save the land from the evil queen? As Mary began lowering you towards her backside, you began to beg and plead that she release you. Your pleas however, were ignored as she parted her massive rear and dropped you in. She slammed her cheeks together as you fell in, your head poking out from in between them. "Don't want my husband suffocating now do I? Don't worry though, now that you're there, you'll be safe!" Mary said as you felt your penis being moved. Mary wiggled her backside a bit and finally lodged your penis into her anus. You could feel shivers go up Mary's spine as she began to play with her butt, rubbing it sensually. Your penis began to slowly move in and out of her hole, which surprisingly was much different from the rest of her body. It felt very soft, almost like jelly. You began getting close to your breaking point as Mary began rattling your penis around inside of her, you struggled hard but your arms and legs were bound by the insides of her buttcheeks. Sandwiched between them, you could only give up and experience the rest of the pleasure that Mary would bring you. You both orgasmed at the same time, Mary had a hard time remaining standing but managed to regain her composure. "..Wow.. That was amazing! You're no ordinary human, that's for sure! You've got some high quality stuff in you!" Mary said as she picked up her basked and began to wade through the earth once more. "Cmon, let's go home!" Mary said as she began to make her way to your new home.
You began to sob quietly as Mary "walked" home. Her butt rhythmically bounced and jiggled as she walked, and with your penis still inside of her butthole, massage you. Before long, the bouncing made you cum again into her, and again. You were being milked just from the simple action of Mary walking. As she hummed a happy tune, you finally accepted your fate to be this Earth Elementals husband.
You spend the rest of your life sandwiched between Mary's buttcheeks, and while occasionally you are taken out for food and non-anal sex, you come to love your home. The feeling of being trapped between this mini-giantess of an Earth Elemental's buttcheeks is a feeling that you couldn't describe, and the immense pleasure you get just from your penis rattling around in her butthole from her walking was the best sensation you had ever felt. Maybe you could have saved the land, but you were much happier spending your life in between your gorgeous Earth Elemental wife's buttcheeks. And she felt the same way, always making sure to get your opinion before she did something... Except for sex or releasing you of course, she let you know that she was the boss there, but the way you felt while having sex made you not care at all.
You were happy to let her dominate your life.