Kun is a friendly Japanese honorable attached to names.

Its role is similar to -San (for adults) or -Chan (for children) but -Kun is used for your buddy.

Mr. Tanaka is Tanaka-San

Little Billy is Billy-Chan

My buddy Danny. Danny-Kun.

However, I thought that the Chan in 8-Chan was an abbreviation of Channel (Channel-8), so I don’t know what is going on or if 8-Kun is legit.