Missing 125 and 126 of the bestiary, no luck with trying to google translate the wiki.
Both no. 125 and no. 126 belong to the mysterious rabbits.
So remember that they are super rare monsters (yellow colored sprites on map).
Therefore going to sleep before looking for them is adviceable as it might be neccessary to spawn/respawn them.
Also important to note is that different kind of rabbits can spawn as super rare enemies in the same location.
See 1st picture set in the screenshot for no. 126 down below: 2 different rabbits in one area at once even.
So just finding one of the other rabbits in that area does not mean that no. 125 or 126 do not spawn there.
It just means you had bad luck with the spawn.
Hence load your save and sleep again or simply sleep again and then go back to the area in hope of getting the correct spawn.
I had to do that for no. 126 in the first location 3 times, too.
No. 125 is Gold Rabi (the golden rabbit) - the easiest location is location c - found at:
a.) Starfall Tower - Go to "Kiyotama near summit" and head north. Then in the space area take the path to the right and follow it till the screenshot - picture pair 1.
b.) Crash Castle - the room where you find the Zand Slayer (Greatsword). - See screenhot picture pair 2
c.) The mountain in the East - Go to "Path to the East" and then there head to the mountain. The Gold Rabi is in the area where you fight the Death Circus (or what those clowns were called). - See screenshot picture pair 3
d.) In the ocean of storms (the ocean dungeon you enter from the bridge of the World Church HQ) - In the room directly before the boss. See screenshot picture pair 4.
No. 126 is Lucki Rabi - Easiest location is b - found at:
a.) AGAIN: In the ocean of storms (the ocean dungeon you enter from the bridge of the World Church HQ) - From the starting position go north twice to end in the area of the first picture set of the screenhot below.
b.) Furuhana Great Bridge - In the area where you start simply go to the lower half and it is right there. - See picture set 2 in the screenshot below.