You could start by looking on dedicated anime and manga fan communities. Sometimes, fans create and share their own works like this 'read d gray man reverse novel' within these communities. Also, search engines can be your friend. Just type in the exact name and see if any relevant links pop up. However, be cautious of potential copyright issues or untrustworthy sources.
If it's an official work, you should check the official 'D.Gray - Man' channels or websites. But if it's more of a fan - created piece, then the best bet is to look in the corners of the internet where 'D.Gray - Man' fans gather. This could be forums, Reddit communities dedicated to the series, or even specialized fan - fiction archives. Keep in mind that the availability might be limited and it may not be easy to find.
You might try looking in specialized anime or manga stores. They often carry a wide range of related novels.
I'm not entirely sure as it might be a relatively niche or fan - made work. It could potentially be a reverse - engineered or alternative take on the 'D.Gray - Man' story. Maybe it focuses on different perspectives of the characters or events in the original 'D.Gray - Man' universe.
I'm not entirely sure as I haven't read it in detail. But generally, it might be related to the 'D.Gray - man' series, perhaps exploring the story from a different perspective, like reversing the normal flow of events or focusing on the antagonists' side more.
You can try fanfiction.net. It has a large collection of 'D Gray - Man Fanfic'. There are various stories with different themes and writing styles there.
Allen Walker is surely one of the main characters. He is a key figure as an Exorcist with a complex past and a connection to the Noahs. Then there's Lavi, the Bookman Junior, who is always observing and recording things. And Lenalee Lee, an Exorcist with strong powers and her own emotional journey.
The 'D Gray Man Reverse Light Novel' often delves into the complex world of the D Gray Man series. It might explore the backstories of the characters, their relationships, and the overarching plot related to the battle between the Exorcists and the Noahs. It could also introduce new aspects of the dark fantasy world filled with Innocence and Akuma.
FanFiction.net is a great place to start. There are tons of D Gray - Man fanfictions there. Just search for the relevant tags and keywords.
Another place to check is FanFiction.net. There are a lot of D Gray - Man fanfics there as well. However, the quality can vary more compared to AO3. You might need to sift through some to find the really good 'critical point d gray man fanfic' you're looking for.
Another option is to check out some D Gray Man - focused fan communities on social media platforms like Reddit or Tumblr. Sometimes fans will share their own fanfictions or recommend ones they've read. You can also post a request asking for Allen and Road fanfictions, and chances are, some friendly fans will point you in the right direction.
You can try fanfiction websites like Archive of Our Own (AO3). There are a large number of D Gray - Man Yullen fanfics there. You can search using relevant tags to narrow down your results.