Seal Of The Primal Rage

Name: Seal of the Primal Rage
Rank: A
Element: None
Type: Fuuinjutsu
Description: This seal was given to Maru by his creator Fujinaro Hojo to help him mold Maru into his instrument of destruction. The seal sacrifices some chakra in exchange for stamina, speed, strength, durability, which is increased by the level of one-rank, and covers Maru in a disturbing black chakra.
Weaknesses: Maru is thrown into a blind, animalistic rage with only two things in mind, destruction and death though they sacrifice logical thinking and control over to their animal instincts. The seal, when activated, requires Maru to sacrifice half of his total chakra stores to use. It also causes pain to Maru every once in a while, causing him to grab his left shoulder, where it is located.
Picture:

Name: Dance of the Primal Rage
Rank: A
Element: None
Type: Kenjutsu
Description: After Maru is under the influence of the Seal of the Primal Rage and is surrounded by numerous enemies, Maru will use whatever bone weapons he has on hand, which is usually his bone knuckle claws, he will proceed to charge head-on into the fray at top speed and start slicing and slashing through his enemies, spraying the area in a shower of gore and blood as he tears through all his enemies like a mindless, raging animal. If he uses this one-on-one, he will proceed to charge head-on at his enemy and slash at them continuously with his bone knuckle claws non-stop using his full speed and strength.
Weakness: Maru attacks constantly with no pattern or with no individual target. His movements and attacks are random and not really focused so all it takes for someone to dodge and counter is to be faster then he is.

Ok, I can understand the jump in rank because of this technique, but how much chakra does he need to sacrifice and what are the drawbacks? o.o

Added in the answers to your two questions.

Ok, I can see this working since he would only be able to use this once or twice.
Approved unless someone says otherwise