I want to pick up the manga from where the anime left off, what chapter or volume should I start at?
The anime ends at chapter 100 of the manga. Below is the last 2 pages of chapter 100.
The anime is generally faithful to the manga (the source material) in terms of important plot points. The anime is quite close to the manga for the first few episodes, then it starts to skip many events in the later half. Notably:
- Mizuka arc, where Murakami and the girls tried to escape from Mizuka, a rank AAA magic user with precognition ability. Mizuka's power can project herself into the future, where she interferes with people's decision to make her vision comes true. The anime skips the whole arc.
- Yuki Tsuchiya, debuting during Mizuka arc as a new employee of The Organization, is skipped in the anime along with Mizuka arc. In the manga, she serves mostly as an excuse to let readers have a look inside The Organization and their treatment towards magic users.
- Kitsuka, who is Murakami's student and has a crush on him, followed Murakami and the girls on their trip to the beach in the manga. This is omitted in the anime. Although this detail being removed doesn't affect the ending of the anime, it is connected to the story after chapter 100 and may confuse you a bit.
- Many details in the last few episodes of the anime are trimmed.
Therefore, I recommend everyone to take a look at the manga for the full experience.
According to this site the anime ends at chapter 100 of the manga
(left side, 8th entry)