I don't believe a masterpiece requires a epic story or a deep narrative or any distinct defining premise to justify itself. Act-age's story is structured like almost any other shounen, a main character with a special talent and goes through various arcs growing and improving their craft to become the best at what they do.

What truly struck a chord with me was the art. The art on its own is impressive, but its certainly not as streamline and polished as Murata's work in One Punchman or as detailed as Miura's Berserk. It's very hard to explain it without having seen it for yourself, but the beauty of Act-age's art is that it enhances the narrative and characters beyond just illustrating them. After all, why draw manga when you can tell great stories through books or show cool action scenes in anime or movies. Manga is a medium that captures a single moment and must portray a characters emotions and energy effectively within the stillness of the panel. I feel Act-age does this better than other manga I've read, as every emotion an actor or actress expresses, joy, anger, sadness, love, and pain, can be seen and understood so clearly, I get chills. Every emotion for every character is expressed uniquely. The sadness expressed by one character is not the same sadness expressed by another character. You can see Yonagi grow as an actress not just by the roles she plays and the techniques she learns, but by the way her expressions change. Its this sort of level of conveyance and mastery of the medium that breathes so much life into every character.

This isn't even something you need to realize to enjoy the manga. I didn't even notice it on my first read, but I think what makes things like this a masterpiece is whether you conscious or it or not, it evokes an emotion you've never felt before. I think epiphanies like these are what define a masterpiece, but regardless of whether you felt the same emotional connection with the series that I had, I think this is a great read for any shounen lover.