It could be Nagisa. Since he is one of the central characters in the original series, he would make a great time - traveling protagonist. He could travel back in time to gain more skills or knowledge to better assassinate Koro - sensei, or he might go forward in time to see the consequences of their actions in the classroom.
One of the main themes is growth. The students in the story experience significant personal growth throughout their time with the teacher. Another theme is the value of education, as the 'assassination' lessons are also a form of unique education. And there is also the theme of friendship that develops among the students as they face challenges together.
The themes include growth and transformation. The students start off as rather ordinary kids, but through their interactions with Koro - sensei and the challenges of the assassination plot, they grow in many ways. There's also the theme of acceptance. They come to accept Koro - sensei for who he is, even as they are still tasked with killing him. And there's a sense of hope throughout the light novel, that no matter how difficult the situation, things can get better.
One of the main themes is the relationship between students and their teacher. In this graphic novel, the teacher is an unusual figure who the students are tasked to assassinate. Another theme could be self - growth. As the students strive to achieve their assassination goal, they also grow personally. Also, there is the theme of friendship. The students bond and cooperate with each other throughout the story.
The 'Assassination Classroom' is about a powerful octopus - like creature that destroys a large part of the moon and threatens to do the same to Earth. He becomes a teacher of a class of misfit students. The students are tasked with assassinating him within a year. As the story progresses, the students grow both in their assassination skills and as individuals. They form bonds with their strange teacher, who also teaches them valuable academic and life lessons.
One of the main science fiction elements in 'Assassination Classroom' is the character of Koro - sensei. He is an octopus - like being with extraordinary powers, which is a very imaginative and science - fictional concept.