Light Yagami's death in the manga occurs because Ryuk, the shinigami who gave him the Death Note, decides to end his life. It's a result of Light's descent into madness and his attempts to evade justice.
Yagami was the protagonist of the Japanese suspense manga Death Note. He was the son of the police chief, Night God Soichiro, and came from a wealthy family. In the manga, Yagami was portrayed as a perfectionist with a beautiful appearance, all-rounded sports, excellent acting skills, and strong psychological quality. He had superior intelligence and malice, and was considered a perverted criminal. Night God Moon's abilities included an excellent mind and a stable mind. He could design a plan to drive a wedge between the police and the enemy, and he could remain calm while processing a large amount of information. He pursued a new world without crime, believing that the world was decaying. Night Goddess Moon's personality and fate were deeply explored in the Death Note. He was a well-loved character because he represented the possibility of indulgence, but he also experienced many failures.
Iori Yagami was a Japanese manga first released in 1988 by Goro Taniguchi. The novel was about a martial arts themed story. The protagonist, Iori Yagami, was a young warrior who embarked on an adventure to protect his homeland. Iori Yagami was one of Goro Taniguchi's representative works and was also known as a classic in Japanese manga.
In many fanfictions about Light Yagami and Misa, their relationship is often complex. Light initially uses Misa for his own ends in the 'Death Note' story. He manipulates her feelings because of her Shinigami eyes which are useful for his plan to create a new world. Misa, on the other hand, is blindly in love with Light. In fanfiction, this dynamic can be explored in different ways. Some might show Misa slowly realizing she's being used, while others may focus on a more 'romanticized' version of their relationship where Light actually develops some real feelings for Misa.
I'm not sure specifically which 'Kazuma Yagami' in a light novel as the name is not widely known in extremely popular mainstream light novels. It could be a character from a relatively niche or new light novel series.
There are a vast number of fanfics on the internet, and given the creativity of the fan community, it's very possible that there are fanfics portraying Light Yagami as gay. Fanfic writers often take characters from their favorite shows or books and put them in new and different situations, including changing their sexual orientation to tell a different kind of story. These fanfics can range from being well - written and thought - provoking to just being a bit of fun and experimentation. So, if you look hard enough on the right fanfic websites, you may come across one.
Light dies when his name is written in the Death Note by Ryuk. Ryuk, who was the shinigami that gave Light the Death Note, decided to end it as per the rules.