A booklet packaged with Harta volume 46 at select stores. It's an anthology of one-shots from various authors focusing on the theme of 4-koma manga. (Source: Natalie, translated)

A booklet packaged with Harta volume 76 at select stores. It's an anthology of one-shots centering on the theme of younger sister.

A booklet included inside Harta volume 50 of Hakumei to Mikochi manga and illustrations written and drawn by various Harta contributors. (Source: Natalie, translated)

A booklet packaged with Harta volume 2 at select stores. It's an anthology of one-shots from Harta collaborators focusing on the theme cats. (Source: Kadokawa, translated)