Damn, I really need to read a novel with a katana wielding mc Novel, fanfic whatever! Help! PS: NO WEAK WILLED, WEAK, AND DUMB MC
The Black Knight Who Was Even Stronger Then the Hero is one off the top of my head. Protagonist primarily wields katanas. Medieval, Isekai setting.
If it doesn't have to be a webnovel and you are prepared to spend a bit of money, there is the Emily Kane series by Jacques Antoine. The MC practices martial arts barehanded and with a katana.
Dragon's Bloodline gender bender but MC uses swords and katana iirc Kansutoppu! MC uses swords (don't remember if they used a katana though)
I checked the raws of the first 20 or so chapters, but it seems to be a straight sword, since katana doesn't appear anywhere. Still is worth the read.