MTL - I Was a Top Student In Conan, But I Was Actually An Onmyoji - Chapter 151

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Sato Yu is a 12-year-old boy. He is a deprived person. His life is depriving. His step father has a large amount of debt.

Endless sky and infinite space, the cosmos isn’t some paradise waiting to be found, it is full of darkness and danger, death and terror of the great unknown. However, for that glittering swath of blue, we have no fear! For the longevity of men, we have no regrets! Nothing shall stand in our way because it is finally our time, our age! The age of cosmos exploration!

The elf girl, Aria is an adventurer. Her enchanting, lovely features attracts everyone. Her twin peaks are ripened to the point of exploding. Then, being embraced in between those twin peaks was a little animal… his name is Tama.

He looks like to be a cat at first glance, but Aria and her surrounding companions failed to take notice of single detail. Tama, he’s a human who’d reincarnated, given a second chance at life. His true form, it’s not that of an ordinary cat. Instead, he’s a monster of the strongest class, an extremely young behemoth.