User blog comment:Xilinoc/Ch. 684 - The Blade/@comment-28131457-20160728135642/@comment-5398287-20160728190344

Totally agree. Ryuken is one thing, sorta, but I refuse, absolutely refuse to believe that Isshin tagged along with him to just literally watch as he gave his son an arrowhead. Ryuken could've come by himself if that was all Kubo had planned for the dad duo. I'm sure they were supposed to help out with the battles against the final two Sternritter (Lilleflamingo notwithstanding), but then that got shot down once Kubo got the 5-week notice, as it were.