BWAHAHAHAHAHAHAHAHAHAHAHA! ..... Kazuichi might need to include training in more than just judo (perhaps Hokuto Shin Ken ... wait, does it have any non-lethal techniques in it?) in order to face Itsuki's grandfather "in that respect". And chances are "Ojii-san" won't hold back just to see if this young boy is truly worthy of his grand-daughter.
Go for it, Kazuichi-kun - DO NOT HOLD BACK ... IT IS YOUR DESTINY (also, it will be TOTALLY WORTH IT)!
Consider this story, AND its Sequel (whenever it shows up) APPROVED!
Well, I can certainly respect how fast he is to take action once he's decided on something. In just one page, from restaurant to bed.
Great ending though. Well hey man, it may seem impossible, but love and sex can motivate a hentai protagonist to accomplish miracles.
Also, "The battle continues next time"? So...A sequel? Sounds great!