25-sai no Joshikousei
The romance story centers around Hana Natori, an earnest, good-natured 25-year-old woman whose cousin refuses to go to high school. Hana takes her cousin’s place and attends the high school. On her first day, though, Hana’s ruse is discovered by her former high school classmate Okito Kanie—who happens to be the high school’s world history teacher. Summary from My Anime List
B: The Beginning
In a world powered by advanced technology, crime and action unfold in the archipelagic nation of Cremona. Koku, the protagonist. Keith, the legendary investigator of the royal police force RIS. A mysterious criminal organization. A wide variety of characters race through the fortified city as it is beset by the serial killer, Killer B, and a chain of crimes in this suspense drama by director Kazuto Nakazawa and Production I.G. Summary from My Anime List.
Hana Ichinose is a normal 16-year-old high school student. However, there is something different about her: She enrolled in high school one year late! Her classmates are unaware of this, and Hana will have to work hard to catch up with everyone else. Summary from My Anime List.