My Big Sister Lives in a Fantasy World Series by Tsuyoshi Fujitaka

One day out of nowhere, high schooler Yuichi Sakaki begins seeing words above people's heads. It turns out to be the ability to see people's true natures, which he names... Soul Reader! (Actually, his big sister names it that.) The next thing he knows, he's surrounded by people with bizarre labels like "Zombie" "Vampire" and "Witch... moreOne day out of nowhere, high schooler Yuichi Sakaki begins seeing words above people's heads. It turns out to be the ability to see people's true natures, which he names... Soul Reader! (Actually, his big sister names it that.) The next thing he knows, he's surrounded by people with bizarre labels like "Zombie" "Vampire" and "Witch." And before he can figure out what to do about that, he finds himself threatened by a beautiful girl, Natsuki, whose label is "Serial Killer"! Fortunately, Yuichi is not unprepared. His big sister has been training him for this kind of thing all his life. The battle is about to unfold between the bloodthirsty killing machine... and the world's strongest little brother! less

Yuichi hasn't yet unraveled the secret behind his magical sight, but the end of his first school term is still as busy and can be! He's got survival club activities led by his big sister Mutsuko, early morning combat training with the serial killer Natsuki Takeuchi, and a first date with the vampire Aiko Noro (with his little sister tagging along, for some reason)... moreYuichi hasn't yet unraveled the secret behind his magical sight, but the end of his first school term is still as busy and can be! He's got survival club activities led by his big sister Mutsuko, early morning combat training with the serial killer Natsuki Takeuchi, and a first date with the vampire Aiko Noro (with his little sister tagging along, for some reason). Then, in the midst of it all, Aiko reveals that her big brother Kyoya – whose world domination-plotting middle school syndrome has been growing worse and worse lately – has gone missing!! less

Yuichi, and the survival club are finally heading off for their summer training camp, to a luxurious villa in a remote seaside resort. Will anime-style swimsuit episode shenanigans ensue? If his big sister has anything to say about it, yes! But while the gang enjoys some much needed fun in the sun, a darker plot lurks just offshore. The world's strongest little brother is about to face his greatest challenge yet!

Yuichi's not-very-restful summer vacation came to an end, and the new school term isn't looking much better. Immortal demons are trying to kill him, his new teacher is a superpowered sociopath, and all kinds of bizarre events are happening around the school. What does Kanako's new novel have to do with the bizarre goings on at Seishin High? Once again, it's up to the world's strongest little brother, and his highly delusional sister, to find out!

Between a secret battle to reassemble a dismembered evil god and a threat from destiny-altering beings waiting in the wings, the world's strongest little brother seems to have enough on his mind. But there's even more waiting in store for Yuichi Sakaki, and things are about to get more chaotic by the week. Soon, a yakuza gang is stalking his little sister, a demon doll is stalking Aiko, an overzealous archer is stalking him... and that's only the beginning!

As the war for the Evil God's vessels begins to escalate, an even more terrible threat comes to Seishin City. When Natsuki runs away, fearing for her life, Yuichi and his friends try to search for her. Their pursuit will lead them not only a new, deadly enemy... but a final understanding of how Yuichi came to have Soul Reader!

The Divine Vessels War is reaching its conclusion. But with Soul Reader gone, Yuichi wants nothing more than to drop out! But will he really be able to go back to the normal life he's always wanted? And if he does, will Mutsuko ever speak to him again?!