This is an extra volume of Sketchbook manga. It appears to have been released along with volume 3. Except for the first 18 pages, it's not restricted to 4-coma style, so everything feels more open and free. I hear this volume is renowned for its cat chapters, where cats interact with each other in cat-talk (translated for us humans).
Ryou-Fuu comic duo fixing Hadzuki's radi-cassette player was somewhat predictable, but highly satisfying as it gave new insights about the comic duo.
