The appearance of a science fiction story on AMV is unpredictable. It could be anytime based on factors like the creator's inspiration, available resources, and audience demand. So, you just have to keep an eye out for it.
For a love story AMV to be outstanding, it needs a well-chosen song that conveys the emotions of the story. Also, the editing has to be seamless, with smooth transitions between scenes. The quality and clarity of the video clips matter a lot too.
It's hard to give an exact time as it depends on the manga's plot development. But typically, Yuta Okkotsu shows up when certain events and character arcs lead to his introduction.
Since I'm not well - versed in Yuta Tanaka's light novels specifically, it's hard to say for sure. But in general, light novels often have simple yet engaging language, vivid characters, and unique story settings. His works might also follow these trends.