Light's watch

This wristwatch begins as an ordinary gift, handed to Light Yagami by his father Soichiro to mark his finishing of high school. Because it carries sentimental weight, Light keeps it on him constantly, a habit that quietly becomes the foundation of one of his most important schemes.

A hidden chamber sits beneath the face, opening only when the crown is yanked four times in rapid succession, each tug less than a second behind the last. Folded inside rests a scrap cut from the Death Note, paired with a needle so that blood can stand in for ink whenever Light has no pen within reach. He relies on the buried fragment to write while still gripping the larger notebook, a trick that lets him hold onto his memories and seize ownership at will. The film versions streamline the design, letting him simply pry the panel loose rather than work the crown.

Light alone knows how to trigger the mechanism. He uses the concealed scrap to finish Kyosuke Higuchi at the moment of his capture, holding the notebook to lock in his returning memories and reclaim it as owner. The same hidden paper later claims Kiyomi Takada and drives her to set fire to everything around her, burning away proof that she had killed Mello. In his final stand he reaches for the fragment to write down Near, but Matsuda's gunshots stop him and Aizawa confiscates the scrap. The tie-in novel revisits the watch as well: in L: Change the WorLd, the broken timepiece rests on L's wrist as a keepsake of the one person he calls his only friend.