🤎🪽

And after a long day of getting these things for Mikami it would only be LOGICAL that they need to replenish their blood sugar levels to continue filling their duties as Kira and what better way to do that with a Birthday Cake?

Since they still need to be undercover, Light is only relaying a secret message to Mikami about appreciating his efforts in the Kira cause in the form of a signed Birthday Card.

He keeps it on him, probably in his wallet. He forgets about it most of the time, but once and awhile he'll accidentally pull it out and stare at it before continuing on with his day.

Light knowing L's true identity and keeping it close to him the same way L knew Light's true identity and kept him close. It's a mutual understanding between the two, even if L is gone.