Akai Kiba is an anthology doujinshi, published between 2002 and 2014. It featured many one-shots from Tsutomu Nihei and other famous mangaka (such as the author of Bokurano, No Longer Human, Blade of the Immortal and Dorohedoro). The anthology spanned 9 total volumes and was sold at the Comiket.

Collection of short stories based on the Persona Q game, made by various artists. Volume 1 Cover: Itagaki Hako, Illustrations: Ookami Wakana, Takeshita, Mochizuki Kazuomi, Risuno Volume 2 Cover: Itagaki Hako, Illustration: Chitose Asahi

From TokyoPop: The capricious young prince Ael dreams of thrilling adventures that will take him far beyond the cold, confining walls of his palace. Little does Ael know that when he meets the young, petty thief Pixie, he is about to embark on a wild journey that takes him beyond the threshold of darkness--to a kingdom where the most heinous of monsters clash, in a world that spans the limits of reality and fantasy...

Cute, pleasant, profound... "Mansion" with cat manga and illustrations. (Source: Kodansha, translated)

Treasure Hunters - Adventurers who search for buried treasure scattered around the world. In Shinjuku, Tokyo, a young man appears as a transfer student at Kamiyoshi Academy. While he seems like a normal student, he is actually a treasure hunter. His mission is to discover a mysterious ruin hidden deep beneath the school. Accompanied by his new friends from school, he sets out to discover the mysteries of a super ancient civilization. However, numerous traps, monsters called "Kehito" that lurk within the ruins, and the clutches of the "student council" stand in his way! (Source: Arc System Works)

A comedy about a girl who loves to clean, and a rich transfer student who has nothing to do with cleaning. (Source: Shuueisha, translated) *Note: This manga was first released as a One-Shot in Manga Life issue 2020/3, and then divided in 5 chapters when later published online.*