I agree that this 7 chapter arc was too long, too stretched out, and god damn anti-climatic.
But... considering that it was a historical story from a grandfather-type character -- and... well, had he gone any further, it would be exceedingly dark for a gag manga like this... I'll take whatever. As someone else said, too much time investment has already been given into this series to just drop it just because of a horrible arc.