Leveling Up through Eating - Chapter 9.1: Fullness System

This stands at the forefront of strategy guides to Life (a shitty video game)!

The Soaring Dragon Continent is a world of summons, you can only become strong if you become a summoner! Yue Yang, an average high school boy, was suddenly transported into this world. When he woke up, he was greeted with a lot of worried faces and found out that he had assumed another person’s identity. Turns out he’s the good-for-nothing third son of the Yue Family, who had just recently drowned himself because of a failed engagement. Unlike the third son of the Yue Family who was useless in summoning, Yue Yang succeeded in making a contract with a summoning grimoire on his first try, even when the other guy failed for the past fifteen years. Others would have a headache making contracts with beasts afterwards, but countless beasts tried to gain favour with Yue Yang instead, acting like a good kid before him.

Yue Yang the brat, however, didn’t feel grateful at all: “Scram, Mythical Beasts! Do you think you are cool like that? Go away from me now, I only like beautiful summons!”

Even when royal families approached him for his talents, the shameless brat replied, “I’m not interested in government stuff, I’m only interested in beauties!”

- Description from novelupdates

A spin-off of Lillia and Treize, Meg and Seron is a high school adventure/mystery/romance/comedy of sorts taking place in the rough equivalent of the 1950s. The story follows Seron, a stoic and handsome bookworm who is in love with his classmate–a sweet, oblivious transfer student named Meg.

Meg and Seron takes place at around the same time as Lillia and Treize, but knowledge of the main series is not necessary to read Meg and Seron.

An 18-year-old poor college student tried to apply for a job as a tutor but his life almost ended as demons' meal. In his last breath, a mysterious woman gave him a strange power. When he opened his eyes he had turned into a demon with a system that would turn him into… A pervert.

Now he must lived with his dual identity as a model student named Ethan and an incubus named Damian.