satchel
A bag used to carry books and other objects. School students are mostly seen carrying this, but it is also used by business-type people. It has a strap that can be worn cross-body (i.e., the bag is on one side while the strap is looped around the opposite shoulder).
See also
This tag implicates bag (learn more).

Pixiv
Twitter
Bluesky
Weibo
Lofter
Tumblr