This year's 18th issue of Shueisha's Weekly Shonen Jump magazine revealed on Monday that Ryōji Hirano (Bozebeats manga) will launch a four-panel spinoff manga based on Koyoharu Gotouge's Demon Slayer: Kimetsu no Yaiba manga on Shueisha's Shonen Jump+ app and website. The full-color manga will be titled Kimetsu no Aima!, and it will update on the site and app on Sundays. The manga will feature SD versions of the characters from the main manga.
The 18th issue also published the first chapter in a two-chapter side-story manga titled "Kimetsu no Yaiba: Tomioka Giyū Gaiden" (pictured at right). Gotouge is credited with the original work, and Hirano is drawing the manga. As the title suggests, the manga follows the character Giyū Tomioka. The first chapter has 45 pages including a color page. The issue also published a new chapter of Gotouge's main manga.
The main manga debuted in Shueisha's Weekly Shonen Jump magazine in February 2016. Viz Media is publishing the manga digitally and in print in English, and Shueisha's MANGA Plus site is also publishing the manga in English digitally.
Source: Weekly Shonen Jump issue 18 and magazine's website