- Aah! What is that?!
Waking up early in the morning, the first thing I planned to see was the kitchen and the piano standing at the other end of the room. And, as I was almost used to, the hard surface I was sleeping on.
The thing was, I'd been staying at the home of the head of the Royal Guard for a few weeks now. A fishwoman named Undyne.

After I got into the Underground and ran into her in the first place, I was barely able to protect all the vital parts of my body from her magical spears. I thought I was done for, but suddenly this warrior looked at me for a while and said that she liked something about me, so she took off her helmet and told me to follow her. I've been living with Undyne ever since, and she's been training me. She wants me to be her partner in the service. Not that I minded, but I didn't have a choice. I had nowhere else to go, so I decided to accept her invitation, which sounded more like an order.

But back to the present. What was my shock when, instead of the usual picture, I was immediately struck by my... blue skin. No, scales, if you look closely. My normal fingernails, both on my hands and feet, had become many times longer and sharper and had taken on a dark blue color. There were a couple strands of hair on my face, blonde as it should be, but to have it on my face.... Last night it barely reached his eyebrows, but now it was no shorter than shoulder height. His body had changed, too: it was bigger, though still in the same general shape. My T-shirt now revealed my waistband, and my sweatpants were now barely below my calves.
But my waist is narrower and my hips are bigger. That's not the most important thing. The main thing was that my shirt was pulled back by two bulges, small but noticeable. I refused to believe that it was... this was it. But with a poke of my finger, I was convinced otherwise. This soft and firm something was clearly a new part of my body..... What a shame.

Quickly getting down from the table (yes, at Undyne's house I sleep on her kitchen table. Not complaining, especially since, as I've noticed, she doesn't have much furniture in her house at all. I'm pretty sure even the landlady sleeps in no better conditions, given her personality), I quickly grabbed my phone. It wasn't much use without a network in the Underground, so I often used it as a mirror, which Undyne's house didn't have at all. Turning on the front camera almost gave me a shock. I was almost an exact replica of my new mentor. Although my facial features remained the same, I had all the hallmarks of a fishman: fins instead of ears, razor-sharp teeth (I even cut myself a little when I ran my finger over them), and my eyes were completely red with black cat-like pupils in the middle.

I decided I was dreaming. Too much training with this monster fish and I started to dream that I had become one too. But no, trying to wake myself up did nothing, I was still a fishwoman.
- What am I going to tell Undyne now?! - My voice sounded much higher now, distinctly feminine. - It's almost six in the morning, she'll be here soon.....
- Wake up, maggot! - Undyne came out of her room with a bang and interrupted my anxious musings. - To exercise.
Suddenly, she broke off her traditional saying and opened her eyes, noticing me standing in the middle of the room with the phone, staring at her just as perplexed.

- U-Undyne! I can't explain everything... or rather, I can't explain anything! - Dropping the phone, I ran to her in a panic, looking at her pitifully. - Why do I look... like you?

- So that potion Alphys gave me worked? Wow! - Undyne quickly switched from shock to what I was used to and began to look at me with enthusiasm. - Although... I was hoping for a slightly different result.

- What do you mean, a different result? What kind of potion? What are you talking about? - I started to ask in a panic, holding my head as my voice, which I still had little control over, almost turned to a shriek.

- Calm down, kid. - Undine said sharply, shaking me a couple times, holding me by the shoulders. - I'll
explain...

Then the monster-fish told me that because I was having a hard time training with her and couldn't get into her rhythm, she decided to take extreme measures.
She went to a local scientist named Alphys and asked her to give her a drug that would instantly revitalize my body without side effects. And the scientist thought of nothing better than to try to pass on the desire to train through my genes. Using Undyne's DNA, Alphys had managed to create a mixture that, in theory, would give me the personality traits of the fishwoman herself, which would help me find the strength to train. So Undуne decided to put it in my cup of tea last night. And I didn't even feel a thing. But apparently, something went wrong.

- It seems you've done everything that makes you - you, except, strangely enough, your character. - Depressed, I sadly sat down at the table, hugging my head in despair. - I still don't feel determined to exercise, so now I'm also a... a girl... and a... monster.

- What a... - Undуne came up behind me and knocked me on the head. - dummy! How do you not understand? It's not enough that this potion didn't work properly, we'll do it differently. Do you know what an opportunity it gives us to be the same species as you? I'm the one who knows my body better than anyone. Now I know exactly what strings to pull and what... - With these words Undyne, smirking impudently, touched my sides with her fingers just below my armpits. I let out a loud "Ah!" in surprise.
Just like the girls in those anime. - points to press to make you work harder.

- Uh-huh. I get it! Please don't do that again. It, uh. feels weird. - I begged, blushing with embarrassment and strange new sensations.

- Then we understood each other! I'll think about your request if you try hard enough. Or maybe... - the fishwoman hugged me around the waist from behind, pressing her cheek-to-cheek against me. - you'll be begging me... just to touch you there one more time.

- Shut the hell up! Hell, there's no way I'm asking you to grope yourself... - I cut her off, crossing my arms over my chest, but the redness in my face was still there, and the sensation of her touch was still spreading through my body.

- I like this! You've never snapped at me before. - Undyne smiled proudly, teeth bared, and patted me on the shoulder, then took me under the elbow and dragged me toward the door. - Come on, put my boots on now! I don't think your shoes will fit you anymore. And hurry up and go to the gym... Sis~

-Shut... up... - I snarled as I put on my new shoes. Okay, "sis"! I'll definitely think of a way to get back at you!