Though a better possibility was thought out earlier, someone said that the ability kinda uses the thoughts of the person targeted instead of Kuma's to determine the location where he wants to land.
that's what I have been try to say for a long time:-)
@I:
BTW–in asking my husband, (who's from Shimane, born and bred) and who, it must be said, has No interest in this manga (and usually will flat out refuse to help with this stuff), he feels the sentence is as you first read it--that it refers to Kuma, because he says it would be "とばされた本人” if it meant the person who was sent as opposed to the sender, but he doesn't have the raw to look at and felt you may have seen something further in the rest of the page to provide context that would make the sentence ambiguous. (FTR--he was the one who typed that bit of Japanese out--I do not speak beyond rudimentary Japanese)--but can you explain why you feel its ambiguous, in terms of this phrasing? It would be good to know, if possible, if Kuma knows or not, as I'm sure you know. (You can use Japanese if you need to. I'll just ask Masa to help me understand again, lol)
I'll try to answer briefly while Aohige is away (listen to him for a more complete explanation)
tobashita honnin [飛ばした本人] is a simple periphrasis (verb+name) which can be built in 3 ways
a) verb + subject [= the person who blew them himself]
b) verb + object [= the people blown themselves]
c) verb + other generic complement
a) is the simpliest and most used because it gives you the most important information (the subject) while b) and c) are used only when you can easily guess the omitted subject by yourself (lol or when you don't want the person you are speaking with to figure it at all).
Now in this case the possible omitted subject (kuma) can be easily guessed because Kuma is in front of luffy and sentoumaru and he's the only person in the world able to use that technique , so the periphrasis can either be a) or b) type, hence the ambiguity.