Hagun applies a 100% TP bonus to your WS. Example: Using Gekko at 150% TP gives it the tp mod of 250% TP. Because SAM's WS tp mod is simply damage (and not acc like asuran, or crits like jin/rampage), Hagun is a very effective weapon for SAM. Also, because of recent updates and how SE changed the ftp mod for YGK at 100-200%, Hagun has an even larger advantage compared to onimaru/ushikiri/shinsoku etc. Well worth the cost, get it.
Aside from Relic, this is the best GK in this game. If you're a SAM and don't have it, drop everything you're doing at go get it! You will not be disappointed.
just wanted to clear something up with respect to something rajah said: the update that changed the 100 and 200 fTP mods is a penalty to hagun not a bonus: before the patch the difference was 33% (2.0 vs 1.5) now it's 20% but the gain from extra tp over 100 is larger.. but you don't get back to a 33% gap until 200TP (hagun=>300) which you will almost never weaponskill at thanks to sekkanoki.
this is still the best AH great katana you can buy, but onimaru *is* relatively better now, not relatively worse.
In there you will find a lv 80 GK that fits your style from +stp to STR+att and heres the best bit when the level cap goes up again so does the weapon and its stats.
The hagun is a WS king under 75 but when your 75+ and you could have a base weapon has a base of 92 that regardless of the mods on this weapon will out WS it.
There is a reason this fell over 2 mil since the lvl cap went up. so i know i am going to get burnt down by ppl trying to rip you lot off, but save ya cash get an onimaru and then the moogle weapon +6str and +20att or +stp its your choice.
Doesn't work with Sekkanoki, but DOES work on the second hit, meaning you close your self sc with at least 200%. That and the fact SAM is just monsterous at the moment is the reason for the rising cost.