Hello again,
First of all, please keep in mind that I am no expert. I'm just answering out of common sense as a Japanese resident, probably slightly younger than you.
With regard to the suicide troops, could this flag have belonged to a Kamakazi pilot?That's possible, although I don't see anything that specifically suggests that he was meant to fly. There were various kinds of suicide troops including submarine troops. Basically, the idea was that the military was running out of fuel, and with the war-time sacrifice mentality, they sent out troops carrying fuel and bombs for one way only.
It's also possible that Mr. Yoshii was assigned to a suicide troop, but never departed, due to his unit running out of fuel/gear for good or because the war ended.
Another thing that came to my mind, since you say your father landed right after the war, is that Mr. Yoshii never left his home in the first place, due to the war ending or what not. I say this, because it typically took a while for soldiers to come home from their units because of the lack of transportation, and because there was great confusion that occured after the war.
If that were the case, would he have still carried it with him on his assignment, or could he have possibly left it with his family?Well, typically those flags were meant for the soldiers to fold and put in their uniforms for good luck, but I suppose it's up to the receiptant.
The other thing is that most war flags left are not exactly blood-stained, but torn or have turned brown probably due to the harsh environment the holders had gone through. So one can assume that whoever carried the flag your father got hadn't experienced much.
For example, I have a relative who went on "gakuto-shutsujin" in which precious college students were drafted at last minutes. He never went to battle, because he was killed in training while still in Japan, and his flag is as clean as your father's.
By the way, your father has every right to keep the flag that seems to have been properly given to him by the original family, but if you're ever interested, there are organisations working to return these flags. You may be able to find out more through them.
http://obon2015.com/english/Also, here is what I found by Googling Mr. Akasaka.
http://www.warrelics.eu/forum/japanese-militaria/translating-wwii-flag...36 says, "Congratulations on your enterance to the troop."
You know, I just found something interesting, and moving as well. On 33 it says, "I wish you good health" by Mr. Iwasaki (no first names), and that's all he says. This is not at all a typical thing to write when everyone is encouraging him "suicidal honor". The guy must have had a very bold sense of humor, because 32 says, "I wish you fight well." while 31 says, "human bomb".
Anyway, just like all the other flags, this one has a lot of names on it, so it should be easy to trace given the proper time and effort.