Okay, so there's been some confusion floating around, but 'Pluto GL' isn't the title of a novel or series—the 'GL' likely stands for 'Girls' Love,' which is a manga/anime genre. What you're probably thinking of is 'Pluto' by Naoki Urasawa, which is a seinen manga (and now an anime on Netflix) and definitely not a GL story.
It's a sci-fi murder mystery thriller, a reimagining of an arc from Osamu Tezuka's 'Astro Boy.' The main plot follows Gesicht, a robot detective in a future where robots and humans coexist, as he investigates the murders of the world's most powerful robots and their human allies. A shadowy force is systematically hunting them down, and the case is tied to a mysterious entity known only as 'Pluto.' It's a deeply philosophical story about hate, memory, and what it means to be alive, wrapped in a genuinely gripping detective procedural. The mood is more somber and suspenseful than anything romance-focused.
If you're looking for a GL plot, you won't find it here, but if you want a masterfully crafted mystery that makes you think, 'Pluto' is absolutely worth your time. The anime adaptation is also fantastic.