Things I Keep Forgetting - Softbrick in 3DS

When a 3DS with CFW (Luma) cannot boot and it only blinking a blue led once, then it's most likely a softbrick. I'm still not sure the cause of this, but the pattern is, the softbrick happen after we don't close a games and turning of the 3DS. Technically speaking, it's caused by the firmware cannot read the boot.firm on the root of the SD card.

Verifying the softbrick

Check if it cannot boot and the blue led only blink once, and then the 3DS turned-off again
Check if ejecting the SD card fix the boot problem

Fix the softbrick

There are some discussion that the cause is the corrupted boot.firm, so replacing it and other luma files should fix the issue. In my case this is not.

For me, to fix the problem, we need to

Delete the 3ds directory in root dir, this is why I assumed the cause is also related to the game state when turning-off the device.
(Optional) Update the B9S
Update Luma (or use the existing version, but download the files again)

Voila! The softbrick is gone! 🌠