I'm not sure. It might have elements of reality, or it could be purely fictional. Without more context or specific knowledge about it, it's impossible to give a definite answer.
Koi was a very popular traditional cultural symbol, usually depicted as a fish with golden scales. In Chinese culture, koi represented good luck, wealth, and happiness. It was a symbol of many families and businesses. During festivals and celebrations, people would make koi ponds and release koi fish in hopes that they would bring good luck and happiness. Koi carp were also widely used in cooking and medicine. They were considered a kind of fish with magical effects.
One great thing about this light novel could be the themes it explores. It may touch on important topics like friendship, growth, or the struggle between good and evil. These themes can make the story more relatable and thought - provoking for readers.
I'm not sure specifically as I haven't read this light novel. It might be about a character who gets involved (makikomarete) and then is transferred to another world (isekai teni suru).
We often call lucky people koi, but in fact, koi are not constellations but mythical creatures. According to legend, koi were creatures with good luck and longevity that could bring luck and blessings to people.
Astrology did not explicitly mention the connection between astrological signs and good luck. On the contrary, constellations were more used to study people's personality, characteristics, fate, and other factors.
Therefore, no constellation was a real Koi constellation. Good luck depended on one's efforts and actions, as well as the living environment and opportunities.
It could be the setting. Maybe it's set in a really unique and unusual place compared to other light novels. For example, it might have a very distinct magical or fantastical world.
Since I'm not familiar with the novel directly, but in general isekai novels often have themes like starting anew in a different world. So it might have a theme of the protagonist getting a fresh start in the isekai world.