Okitegami Kyouko no Bibouroku

The second instalment of the Boukyaku Tantei Series. 

A young man, Oyagiri Mamoru, works as a security guard at a museum. 

Whenever he visits the area he guards, there's always a beautiful white-haired woman who stops in front of a particular painting. She is Okitegami Kyouko, also known as the Forgetful Detective. They were only supposed to be a guard and spectator until a number of tough cases involving art occurred—. 

(Source: Kodansha, translated)

Twenty-five-year-old Kakushidate Yakusuke suffers from the fate of constantly stumbling into various crime scenes and ending up being the main suspect.

His last resort: Okitegami Kyouko the "Quickest Detective." However, Kyouko suffers from a strange case of amnesia; whenever she falls asleep, she forgets everything that happened the previous day, making her solve the mysteries within one day. 

*Note: Includes 4 extra chapters.*

What if Monogatari's Ararararagi, Zaregoto's Ii and Jun "Humanity's Strongest" Aikawa, and Okitegami Kyouko no Bibouroku's titular forgetful detective all attended school together? In 2002, NisiOisiN won a Mephisto Prize prize for his debut novel Zaregoto, Book 1: The Kubikiri Cycle. Part of the 15th anniversary celebration will be 4-panel crossover gag manga Seishun Kijin-den! 240 Gakuen (240 is a pronunciation pun - 240 can be read as "Nishio," so "Youth Oddball Story! Nisio Academy").

(Source: Crunchyroll)

A series of crossover stories between characters from Monogatari and characters from Nisio's other works. Originally, 4 crossover short stories were released during the theatrical screenings of each Kizumonogatari movie. The stories were bundled up into Mazemonogatari, and included 3 unreleased stories.

Includes 15 stories:
Kyouko Balance
Jun Build
Nomi Rule
Mayumi Red Eye
Kuroneko Bed
Risuka Blood
Hitei Clear
Iori Fugue
Shiogi Ranger
Akari Triple
Rizumu Rock 'N'
Mikoko Community
Kuu Invisible
Rai Roulette
Magakoro Finisher