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It's questionable whether that one was an AU though. Not even because of the threesome but because how weird is it that the heads of the Japan, HK and Russian underworld was just happily chilling at an onsen and Yuri was also there all chill like hey guys it's me, you tried to kill me back then but I'm here it's all good.
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questionable indeed, since the chap. came after the Hong Kong arc. During that arc, Yuri was shot by I think , Asami? and fell into the sea.
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I don't see Asami and Feilong alone together, though. But I can see him share kinky moments with Akihito and having Feilong participate once in a while. Like they start bickering, then Akihito prevents them from drawing guns, and BAM! they team up to mess with Akihito and it turns into a hella kinky moment.
Ok so now that you two get along better, it's time for a THREESOME!! ლ(´ڡ`ლ)