I didn't closely read the comments on the last post, so sorry if I'm repeating anything. I'm not super knowledgeable about that particular category of visa, but with both a student visa and a work visa there is a 3-month grace period after your school/work ends before you have to leave. I've heard the grace period is a bit longer now due to corona. I did a half-semester at my Japanese school on a student visa a couple years back, but since I wasn't doing a full semester, it didn't count towards my visa. My school told me it was fine and I wouldn't be overstaying or causing any future problems for myself, but if I were doing a part-time job I wouldn't be able to continue because my visa wasn't technically "valid."