[Autumn]

I think it would be more fair to the other katanas if they gained more proficiency in battle other than having solely on-kill effects, they are not at all considered much compared to the likes of Raijin, or even Hisen now, so I think it reasonably stands to amp up their potentials to have a bit more usefulness for the swordsmen who don't want to be lightning themed (rare as they may be.)

Here are my current suggestions:

Kouenjin / Crimson Lotus

Potential Skill - Crimson Lotus
Kouenjin's Potential Skill. The Kensei skill Hidden Cut's effect changes in the following ways; Damage becomes Fire magic damage. Monsters who are defeated by this effect explode, knocking away field objects and dealing Fire magic damage equal to Hidden Cut's damage in a 3 Range circle around them.

Changed to:

--Enemies who are targeted by this effect explode, knocking away field objects and dealing Fire magic damage equal to 50% of Hidden Cut's damage in a 3 range circle around them.

If an enemy is killed by this effect, inflicts certain defeat.

Yukijin

Potential Skill - Ice Lily
Yukijin's Potential Skill. The Kensei skill Hidden Cut's effect changes in the following ways; Damage becomes Ice magic damage. Monsters who are defeated by this effect turn into Ice Points and create Ice Sheets in a 2 range diamond around themself, which last for 3 rounds each (The LV for the Ice Point created is 10).

Changed to:

Enemies who are hit by this effect may be frozen for 2 rounds (with an infliction check), and create Ice Sheets in a 2 range diamond around themself, which last for 3 rounds each. (Frozen Level = 25)

If an enemy is killed by this effect, gain Ice Point Guard status for 3 rounds.

Akujin

Potential Skill - Dark Moon
Akuijin's Potential Skill. The Kensei skill Hidden Cut's effect changes in the following ways; Damage becomes Dark magic damage. Monsters who are defeated by this effect melt, becoming Dark Water tiles in a 2 Range circle for 3 rounds.

Changed to:

--Enemies who are targeted by this effect gain Dark Resistance Down. (LV = 15, can stack twice), monsters who are defeated by this effect melt, becoming Dark Water tiles in a 2 Range circle for 3 rounds.

Sanjin

Potential Skill - Mossy Grave
Sanjin's Potential Skill. The Kensei skill Hidden Cut's effect changes in the following ways; Damage becomes Acid magic damage. Monsters who are defeated by this effect melt, becoming LV 30 Poison Pool tiles in a 2 Range circle for 3 rounds.

Changed to:

--Enemies who are targeted by this effect begin to melt, gaining lvl 5 Acidity for 3 rounds, increased to 10 against heavily armored enemies. Monsters who are defeated by this effect melt completely, becoming lvl 30 Poison Pool tiles in a 2 Range circle for 3 rounds.

Either way it goes, I do think they should sit up there in the cool and viable squad alongside the aforementioned Hisen and Raijin.

[Lolzytripd]

I like these, though I always thought that Crimson lotus should also have cinder tiles.

Also It would be nice if they were differentiated a little more.

Remove the finesse tag from Kouenjin and give it Flamelit

Add Cold to Yukijin

Make Sanjin Scale Guile main stat....

[Entropy]

Full support. These effects seem pretty tame, freeze is a little bit fucking spooky but Yukijin has nothing else going for it, so let it have fun.

[Poruku]

Yes yes yes yes yes

[the REAL Minos Prime]

Also make them scale based on their element. Kensei needs more synergy with other classes.

[Snake]

Seems a bit uneven on what each effect does, and while I agree that they're literally in a state that anything they gain can help, why not go with this:

- Kouenjin
>> Hidden Cut: Deals bonus Fire Damage after the slash damage, equal to 100% of your Fire ATK, and automatically cast Explosion centered around the first enemy proc. (Sword will be the casting tool.)
>> On-Kill: All friendly Bombs and Explosions immediately trigger, and you gain Nerhaven LV4 for 4 rounds.

- Yukijin
>> Hidden Cut: Deals bonus Ice Damage after the slash damage, equal to 100% of your Ice ATK, and automatically cast Famiuga centered around the first enemy proc. (Sword will be the casting tool.)
>> On-Kill: Automatically use Expanding Ice for free, with your Sword's Power replacing a Fist weapon.

- Akujin
>> Hidden Cut: Deals bonus Dark Damage after the slash damage, equal to 100% of your Dark ATK, and automatically use Wretched Oil centered around the first enemy proc. (Sword will be the casting tool.)
>> On-Kill: All enemies within 4 range of the defeated enemy will be Feared for 4 rounds, and afflicted with Imagin's Despair.

- Sanjin
>> Hidden Cut: Deals bonus Acid Damage after the slash damage, equal to 100% of your Acid ATK, and automatically cast Acid Rain centered around the first enemy proc. (Sword will be the casting tool.)
>> On-Kill: All enemies within 4 range of the defeated enemy will take 25% of the defeated enemy's max HP as Acid magic damage.

[Autumn]

I would really desire to be able to use Kouenjin but there is little reason to, please I am begging for a buff to these potentials.

[zericosmic]

These ideas are incredibly based, would love to see more katanas used.

[Dezark]

I'm up for these ideas from Autumn, they look really cool and seeing some love for the katanas would certainly be nice!

[FaeLenx]

A rare moment where I'll hop in and see absolutely nothing wrong with a suggestion. +1, please make some of these trash weapons better in a way that DOES just offer more build diversity like the post suggests.