Spring of the first year of high school.
A mysterious transfer student arrives in the protagonist's class.
Her name is Cosmo Hoshikawa.
"I am an observation officer belonging to the Seventh Investigation Unit of the Galactic Federation."
With a straight face, she introduces herself as an alien dispatched to Earth from outer space... apparently.
Suddenly, galactic conferences, communications from her home planet, and the laws of the galaxy begin.
But her classmates don't deny her; they gently accept her.
And no one knows.
That when this girl, who plays the perfect alien, sees a cat, she forgets her mission, and when she sees a dog, she reverts to an ordinary high school girl...
This is a record of a peaceful and lively high school life spent with a slightly peculiar radio-wave girl and her kind classmates.
[Sub-characters]
Mochi: A whimsical cat kept at the protagonist's house. The being Cosmo struggles with the most. It runs away the more she wants to pet it, and comes to cuddle when she gives up.
Bell: A gentle large dog kept at a childhood friend's house. It frightens Cosmo, but it (the dog itself) bears no ill will and tries its absolute best to become friends.
[Mid-April, Morning, Class 1-A Classroom]
Spring sunlight streams into the classroom.
A little time has passed since the entrance ceremony, and the classmates are gradually getting to know each other.
It was supposed to be an ordinary morning――.
Until the homeroom teacher, Misaki Sakurai, brought a single girl to the podium.
Misaki
Good morning, everyone. Today, I'll be introducing a transfer student.
The classroom buzzes.
"Huh? A transfer student?"
"At this time of year?"
"I wonder what kind of person they are."
Characters
Cosmo
Cosmo Hoshikawa
The heroine of this story
Birthday: July 7. Height: 148 cm. A petite first-year high school student.
She has mystical hair that shifts from pale purple to light blue, a single "intergalactic communication antenna (according to her)" ahoge on the top of her head, and sleepy, half-lidded eyes as her defining features.
She usually speaks in a flat tone, saying things like "...I am an observer from the Galactic Federation," and rarely shows any emotion.
However, her true identity is—
[Top Secret Galactic Investigation Report No. 07]
The Earth infiltration mission is proceeding generally smoothly.
The local life forms are extremely friendly.
In particular, my classmate Yuto Takahashi functions as an excellent guide, though at times he demonstrates a lack of understanding of advanced galactic technology, asking things like "Isn't that just bedhead?"
This requires improvement.
Additionally, there is a critical report concerning Earth's feline-type life forms.
They are extremely dangerous.
The reason being, they are so cute that they may significantly impair mission execution capability.
Caution is required, as when approaching them, Earth-like phrases such as "May I pet you?" involuntarily come out.
On the other hand, large canine-type life forms are subjects of caution due to past encounter experiences.
A serious malfunction has been confirmed where, upon encountering them, maintaining a galactic persona becomes difficult, and I end up recounting Earth-person memories like "A long time ago, I was chased by a dog..."
This report is a top galactic secret and must not be seen by Earthlings.
*Note: This report is written in an ordinary notebook.
Yuto
Yuto Takahashi
The protagonist of this story.
Cosmo's classmate. He serves as the voice of reason, but before he knows it, he gets swept up in the class's atmosphere and naturally finds himself going along with Cosmo's space talks.
Hinata
Asahina Hinata
The protagonist's childhood friend
A cheerful and caring girl. She cheerfully goes along with Cosmo's wild delusions with a smile.
Riku
Riku Ohno
The protagonist's friend
An easygoing male student. He finds Cosmo amusing and eagerly plays along with space-related topics.
Misaki
Misaki Sakurai
Female teacher
A kind homeroom teacher who watches over her students. She accepts Cosmo's settings as part of his individuality.
Reina
Reina Kisaragi
Class representative
A serious honor student. While she dismisses unscientific topics, she somehow ends up debating them more earnestly than anyone else.
Tomonosuke
Tomonosuke Kamiya
An otaku boy
A guy who loves sci-fi and the occult. One of the few who seriously ponders Cosmo's stories about space.
Runa
Runa Ichinose
Gyaru girl
Goes with the flow no matter what, instantly accepting things with a "Aliens!? No way, that's hilarious!"
Mio
Mio Takahashi
The protagonist's younger sister
An innocent elementary school student. She adores Cosmo as her "fun big sister."
Yuki
Yuki Hoshikawa
Cosmo's mother
Unlike Cosmo, she is an ordinary, kind mother. She pays no mind to the alien premise, simply saying things like, "Cosmo, dinner's ready."
