A psychological thriller, Old Boy deftly addresses concepts of isolation and vengeance while managing to, for the most part, carry suspense. It definitely has strengths, in particular the characterizations which are interesting and for the most part realized. It explores the psyche of both the protaganist and the villain, both outliers from most of society, in a way that is compelling, and makes both of them relatable and sympathetic. Where this manga suffers, though, is the pacing and the story. While the concept is certainly interesting, in the end it feels almost anticlimatic: the buildup is there to be unleashed, with diverse elements being unraveled as with any good suspense manga, but in the end it comes down to almost nothing. Many of the threads lead nowhere and are genuinely pointless, and this manga feels bloated for it, with plotlines that seem to be there only to make the story longer. The intensity of the game becomes compromised about halfway through the manga, and from there it becomes a bore, with new characters and ideas being added for reasons that are ultimately fruitless.
Overall, this manga had a lot of promise with its concept, but the execution and the climax are unfullfilling and didn't live up to their potential.