In the world of card games, it's pretty common for the world to be destroyed by them. I, Tanahuda Mitsuru, reincarnated into such a world and finally achieved my dream of becoming the manager of a card shop. In this world where people enjoy card battles, I just wanted to watch them up close. However, from the outside, I seem to look like the previous manager, who has solved many major problems and watched over the children as a leader. But, In reality, I’ve never solved any major problems at all. This is the story of a reincarnated person who, after becoming the manager of a card shop in a world where card games are prioritized above all else, is mistakenly believed by those around him to be the previous manager who has solved major incidents in the past—when that’s definitely not the case.

“Why do you keep making me misunderstand you like this!? My affection level can’t go any higher than this, you know!?” (← said by the princess with the greatest beauty in the kingdom) The puppy-like beautiful girl sitting next to me who’s grown attached to me… turns out she’s actually a princess. I'm Heim, and I enrolled as a scholarship student in a magic academy full of nobles. Unbothered by being looked down on as a commoner, I devoted myself to honing my magic—until one day, I accidentally learned the national secret of the princess’s true identity. While carrying this secret, I end up pretending to be her lover to protect her from the arrogant nobles targeting her. “Heim-kun, I want to be with you! I want to, I want to, I want to, I want to!” Alone together, close enough to touch with homemade bentos. In front of me alone, the princess’s demeanor grows sweeter and sweeter— A royally sugary love comedy begins! (Source: Kadokawa, translated)

https://www.cmoa.jp/title/342049/