The following is an abbreviated list of Japanese websites on comics, graphic novels, and anime, known in Japanese as manga (漫画). The lists below are based on a much more extensive and well-researched guide compiled by Michiko Ito, Japanese Studies Librarian at the University of Kansas: https://guides.lib.ku.edu/c.php?g=94978&p=7378433. Note: The websites below may contain adult content that are considered inappropriate for educational reading.
Open Access Comics
Short manga stories (読み切りの作品) selected by COMIC メテオ
Links to a selection of short and complete comic titles.
マンガ図書館Z = Manga Library Z
Formerly known as J komi, this website provides access to out-of-print comics with authors' permission. All are free.
Sukima (スキマ) is an e-comic store but includes some free comic works and free previews of commercial comics. Registration may be required. This link leads directly to the list of titles which are all free.
Designed for SNS. This is similar to a short comic published in a newspaper. 1 page-length episodes are added and updated frequently.
You can find manga in The OSU Libraries catalog with any one of these methods