You get the amalgam [Daikyu] mod from the ropalolyst, 5 amalgam mods drop in total, each with a 20% chance.

For infinite life support, pair this with a [Nikana] and on every melee hit you get 3% life steal. It's 3% of the damage dealt per hit. Doesn't sound like much but in reality it's equal to a full heal on most frames.

Does not work on two handed nikanas like [Tatsu] but will work with the sephan zaw strike.

I often run this with just the two amalgam mods so I have increased sprint speed and infinite healing and never actually use the weapon.

You certainly don't need to plough 7 forma into the weapon if all you want is the healing.