I've read a book about the history of Japan and I found that there is almost no information about people that existed during those 2 periods and instead of that you find a list of emperors that didn't exist in real life. I'd like to know more about that two periods and not only general information about the whole place. I'd like more specific information for understanding more. Any book or YouTube channel would be great.
And also I want to know who was the first real emperor of Japan and why is it so difficult to know details about the past of Japan before 7th century.
There is no consensus about "who was the first real emperor of Japan." A notable early emperor is Emperor Keitai, whose rule is said to have begun in 507 AD according to official histories. Keitai's genealogical ties to the previous emperors are strained and it is thought that he may have risen to power during a period of strife at court. We could therefore assume that there was an imperial court around this time, or at the very least an ancestor to the later established regime, but it is unknown how powerful this court really was, and the date of 507 is not firm.
The only firm way in which Yayoi archaeology tracks the traditional genealogy is through the Three Sacred Treasures or Imperial Regalia which have been handed down through the generations (some were lost and remade at least once). The three treasures are a sword, a mirror and a magatama jewel. All three of these objects were collected by local chiefdoms during the Yayoi period, and if you visit a Yayoi period archaeological site you will probably see dozens of examples of each. So, in a very vague sense based on the continuous handing down of these objects, there was some symbolic continuity between Yayoi and the early centuries AD. However, absolutely nothing can be said for sure about the form which this took.
When we go back to before 500 AD, there are many ways in which the official histories fail to correspond with outside sources. Most famously, there is the "Queen Himiko of Yamatai" story found in a Chinese source: the names "Himiko" and "Yamatai" sound convincingly Japanese, but other than that this story seems to have no connection to anything Japan records about its own history, and some Japanese writers even claim that the whole story is fabricated. More broadly the name Wa or Na appears in many Chinese and Korean sources, and a gold seal was uncovered in Kyushu with "King of Na" written on it, so this cannot be fabricated, but it is unclear what, if anything, corresponds to Wa/Na in Japan's official histories.
For more information with many fascinating theories about the identity of Himiko, see Jonathan Edward Kidder (2007), Himiko and Japan’s Elusive Chiefdom of Yamatai, University of Hawai’i Press.