One possible plot could be that Light Yagami discovers the existence of demons from the Inuyasha world. He might see them as a new type of 'evil' to be eradicated. He could start using the Death Note on demons, which would draw the attention of Inuyasha and his group. Inuyasha would initially be confused about these strange deaths and then realize that a human is causing them. This would lead to a conflict as Inuyasha believes in slaying demons in a more 'honorable' way and not through this strange notebook's power.
A plot could involve Kagome being transported to the Death Note universe. She accidentally stumbles upon the Death Note and picks it up. Since she has a good heart, she is horrified by its power. Meanwhile, L notices some strange deaths that don't seem to follow the normal pattern and starts investigating. He discovers Kagome and initially suspects her of being the one behind the killings. But as he gets to know her, he realizes there is more to this strange girl from another world. Inuyasha then comes looking for Kagome, which further complicates the situation in the Death Note world.
A crossover with 'Fullmetal Alchemist' could also be fascinating. Maybe Edward Elric discovers the Death Note in his search for the Philosopher's Stone. He would be conflicted because his moral code as an alchemist goes against using such a tool for killing, yet the power it offers could potentially help him achieve his goals in a different way.
A plot could involve a spell gone wrong in the Inuyasha world that opens a portal to the Disney realm. Kagome, being from a more modern world, recognizes some of the Disney elements. Mickey Mouse could be the first Disney character they meet. He helps them navigate this new world while Inuyasha is trying to find a way back home. Meanwhile, Disney villains might see Inuyasha as a threat and try to get rid of him. But Inuyasha, with his combat skills, manages to fend them off. In the end, they find a way to close the portal and return home, but not before creating some new friendships and memories.
One interesting plot could be that Naruto and his friends are on a mission and accidentally end up in Inuyasha's feudal Japan through some sort of magic portal. There, they meet Inuyasha and his group. Naruto's ninja skills could be put to the test against the demons Inuyasha usually battles. And perhaps they team up to defeat a powerful common enemy, like a super - strong demon that neither group could handle alone.
It's a tough call, but it could be Light. If he manages to get his hands on the knowledge of the Inuyasha world and its rules, he could use the Death Note very effectively. He could target demons by learning their names, and since many demons in the Inuyasha world are vulnerable to human - like weaknesses in some ways, his strategic mind could make him a very powerful force. He could even manipulate some of the human characters in the Inuyasha world to do his bidding.
One possible plot could be that Inuyasha and his friends are somehow transported to the world of The Walking Dead. Inuyasha's sword, Tessaiga, could be effective against the zombies as it can cut through almost anything. They could team up with the survivors in the Walking Dead world. Kagome's spiritual powers might also be useful in detecting the zombies from a distance or even purifying them in some way.
In a crossover, the two different power systems would create a really interesting dynamic. The Death Note's power to kill anyone whose name is written in it, and the Geass which can control others' actions. If Light and Lelouch were to cross paths, there would be a battle of wits as they both are highly intelligent characters. Light would be cautious of Lelouch's Geass, and Lelouch would be wary of the Death Note's invisible and deadly power.
Well, in scp death note crossover fanfiction, a cool concept is the clash of different power systems. The SCP entities have their own unique and often bizarre abilities, and when combined with the Death Note's ability to kill just by writing a name, it creates a really chaotic and interesting scenario. Maybe some SCPs would try to find a way to nullify the Death Note's power or use it to their own advantage in their never - ending pursuit of chaos or control.
Well, in 'kaneki crossover death note fanfiction', a possible concept is the way their different worlds collide. Kaneki comes from a world full of ghouls and the CCG, and Light is in a world where he's using the Death Note to change society. If they were to meet, it could lead to some really intense power struggles. Also, the idea of how their respective allies and enemies would react to the crossover is quite fascinating. Kaneki's friends from Anteiku might be completely bewildered by the Death Note, and Light's accomplices might see Kaneki as a new threat or a potential tool.
Well, one possible plot could be that Rick accidentally opens a portal to the Inuyasha universe while trying to find a new energy source. Morty gets dragged along and they meet Inuyasha and his gang. Maybe Rick's advanced technology could be mistaken for some kind of powerful magic by the characters in the Inuyasha world. And Morty could befriend Shippo, since they are both kind of the sidekicks in their respective groups.
Well, one possibility could be that the characters from Ice Age end up in the feudal Japan setting of Inuyasha. Sid could befriend Shippo, the fox demon. They might get into all sorts of comical situations together, like trying to find food in a world full of yokai. Manny, the mammoth, could be mistaken for a strange demon by some of the more superstitious villagers. And Diego might team up with Inuyasha to fight a common enemy, perhaps a powerful ice - based demon that threatens both their worlds.