One popular gachiakuta fanfic might be those that explore the backstories of the main characters in more depth. For example, a fanfic could focus on the early life of the protagonist before the events in the original work, detailing how they developed their unique abilities or personalities.
It depends. If you're reading manga on legitimate websites that have the rights to distribute it, it's not illegal. However, if you're getting it from illegal torrent sites or unlicensed platforms, then yes, it's against the law.
The legality of reading manga online depends on the source. Legitimate platforms with proper authorization make it legal. But most random sites offering free manga are likely illegal and can get you in trouble.
First, you need to have a good understanding of the gachiakuta world, including its characters, settings, and the overall theme. Read the original work carefully.