Koi Fish; A new hero in Paris (Chat Noir x Reader!Mermaid)

Chapter 2- The Kwami

As soon as I walked near my desk, I saw a box:

 As soon as I open the box I saw a ring: 

When I wore it, a bright, white light shone and after that, I see a small creature floating in front of me.

"Finally, I got out of there. I needed to stretch." It said. It's facing me now. I kept staring at it. Is this normal in the human world? It said; "Oh sorry, forgot about you."
I stood there dumb folded. I asked it; "What are you?"
"Oh I'm Kōhaku; your kwamii. You have been chosen to be Paris' next superhero; Koi Fish." He said. He looks like a koi fish. "Say what now?!" I shouted.
"Sh,sh,sh." he said, covering my mouth with his tiny flippers. He continued to say; "No one must know about my existence." 

I nodded my head, showing that I understood. Then I noticed a bubbly feeling. I looked at my hand and noticed that it got wet. I think it happened when he was covering my mouth, I had moved towards my desk, where I had tripped my opened- water bottle on my hand.
"Oh seaweeds." I said as I transformed into a mermaid. 

"Oh sorry about that. I also forgot that when you get wet, your tail appears." He said. I told Kōhaku; "Wait I didn't tell you that. How did you know?" 

 "As soon as you wore the ring, I felt a different kind of presence, not only human, but also a mermaid and I'm so glad!" he responded. I giggled a bit at his response while lying on the floor. I asked him;"So, what kind of powers do I have?" 

"Well your power is called Siren Scream, you would have a really high pitched scream that it could break glasses." He said. i said; "Woah that's awesome!"

"Oh and your weapon is a spear that can be thrown, the tip of the spear can be used as a grappling hook and can also be transformed into two katanas." He continued to say.

(This is how the spear looks like)

"Can I still use my mermaid powers?" I asked. He said; "Yeh, you still can. And also you would also have a belt which will provide water for when you need to attack your enemies. You will be fighting along with Ladybug and Chat Noir." 

"Who are they?" I told him. He answered; "They're Paris' superheroes, fighting crime against anyone who has been akumatized." 

"How will I know who they are?" I said.  He said; "You'll find out."

After my tail dried and got my legs back, all of a sudden I see the sky change from clear blue to being hidden by dark clouds. "I know I'm not familiar with the human world, but this isn't normal."

"A person must have been akumatized. Hurry, to transform, say; "Kōhaku, tail out!" Kōhaku said. I nodded and said;

"Kōhaku, tail out!"

Transformation:

I placed my hands where my chest is, right hand on left hand, as Kōhaku enters my ring which is on the ring finger of my right hand. After that, I raised my arms high up, the back of each hand touching each other and from my ordinary clothes, from my hands to my feet, they changed into a white cat suit with a giant, orange-reddish dot on my chest, covering everything till the tips of my fingers and toes. Then around my waist appeared a white belt with transparent semi- sphered containers, providing water and holding my weapon. Then, I lowered my hands down in front of my eyes and spread them apart to create my mask, the same colour as the dot. Finally, I did my pose.

"Oh my bubbles! This is so cool! Oh the mission." I said and just like that I started to leap from rooftop to rooftop to arrive at my location.