Nevermind, found it.
Magical Girl Lyrical Nanoha Fanbook Album - Asterisk Story 1.
https://dynasty-scans.com/chapters/magical_girl_lyrical_nanoha_fanbook_album_asterisk_story_1

I remember a Nanoha x Fate doujin that's about communicating if I recall correctly. The scenario is that the real-time galactic communication translation service is under maintenance, so for a few minutes, Fate and Nanoha hear each other in their respective native tongue yet still understand each other a bit (Japanese for Nanoha and Midchildan for Fate).
Edit: It is a oneshot.

last edited at Feb 7, 2024 1:43PM

Raijin is so cute! give me moar XD

(for those who don't know who she is,you better play the psp game .-. )

Or watch the Nanoha Reflection and Detonation movies.

Oh dear... How the hell Nanoha and Fate is going to explain to Vivio about this...

last edited at Feb 6, 2024 1:18AM