@Kefrayba
Ai-chan actually studied in Ai-chan's sleep back in school. That was why Ai-chan was always either first place or second place in class ranking. Unfortunately, it is very exhausting. What you do is basically make use of 'personal time' that Hawking theorized but nobody tried to talk about it because nobody understood it. In your dreams, you are not bound by physical limitation. Your dream time is not linear with real world time. You can have dreams that lasts a century yet only sleep for a few hours while you can have a dream that lasts a week despite sleeping for more than 12 hours.
How do you achieve studying while sleeping? By cramming everything you can all the way up until you can't think anymore. Then, you go to sleep. You will get a nightmare, such as for example, a nightmare about calculus or chemistry and how things connect to each other, but you will learn in your sleep. Stuff in a single nightmare may not be accurate, but you do instinctively remember it when you wake up. All you need to do once you're awake is correct the mistakes your dreams made and go back to sleep to seal the knowledge in.
It's a hell of a study method though. Ai-chan won't recommend volunteering for such hellish training. Ai-chan burned out by 22 years old.