I was asked by Richard to read this and give my input, so here I am.
A hello to Mert, I enjoyed meeting you in New Jersey last month at the Hakkoryu Embukai, hope to see you again.
As I wrote to Richard in a private message earlier, I wish you could read my twelve year old posts on e-budo.com about the "is there aiki in Hakkoryu" subject. I'm still a student, but in hindsight reading my words back then is both amusing and embarrassing.
Hakkoryu was and is a "jujutsu" for the vast majority who study, and the techniques are taught in a way that's not tough to grasp, and this is by design. Receiving a fourth degree black belt in Hakkoryu only means that a person has received and is (according to their Shihan) proficient in the Shodan, Nidan Sandan and Yondan-gi waza sets, which are not lengthy.
That's it. The intent was and is that the individual should be infused with decent jujutsu techniques. It seems that Shodai Soke Okuyama's goal was to prepare people quickly for their own self-defense, which became particularly important for people in Occupied Japan at those times, but reserved an incredible amount of teaching for those who stayed with him and persevered.
For a lot of years I was a frustrated Yondan and sought out the answer to my question "where is the aiki?" Shogen Okabayashi was the one who answered my question and shared with me. He also impressed upon me that I was too stupid to realize it then, and I should work harder in my own school, but like many of us, I had little patience. I was, and still am an idiot sometimes. In the end, his advice rang true for me.
In Hakkoryu, the Shihan Jikiden is the first time we get some lessons about ourselves, the body, what have you. With the Kaiden teachings it goes further.
Sandaikichu (three big pillars) is a whole new ball game. It answered all my questions and now I am the one who feels like a beginner all over again after 33 years.
Is there "aiki" in Hakkoryu?
MAYBE, it depends on you. Good news, it's good jujutsu!
If you want more than that, how far do you want to go?