Both manga are written by Jiro Taniguchi. They have similar art styles and vibe. Both are slice of life manga that have a simplistic story, but have a lot of bittersweet moments that manage to draw out the reader's feelings.
Both are excellent examples of slice-of-life done well. Gentle storytelling, combined with minimal dialogue (allowing the pictures to tell the story), pictures that do indeed paint a 1000 words and an overwhelming sense of peace and harmony, make these a delight to read. The Walking Man has the advantage that it does not have the same gentle melancholy that YKK has, making it a more uplifting read that reminds us all the we need to stop and smell the flowers more often.
Both are slice of life manga written by Jiro Taniguchi. They have simple stories taken from everyday life, but full of emotional moments. In both manga, the main characters try to enjoy life to the fullest by living every moment of it.
The Walking Man and Yama E Iku (in the Anywhere But Here anthology) are extremely similar to one another. Nothing ground breaking happens, but a man just walks around, and takes in the beauty of nature around him. It's about simple things.
Both manga have protagonists that do plenty of walking on their free time. The Walking Man could be summed up as "stop and smell the roses" while BLAME! could be summed up as "stop and shoot the cyborg killing machines".