Here's just a bit of what I have to add to the discussion:
1) As a Jonin medal holder I was able to invite 3 ninja from day one. My bond level is now 53 and I am still only able to invite 3. However, I now have 7 ninjas at my home rather than the three I had day one. This is also 2 more than I had yesterday. It does appear that there is an increasing maximum value of ninjas that can show up, which I think is related to the ninja refreshes they refer to on beloved Ero Sennin's screen. The three you invite are just ones that you absolutely want to show up while the difference from your maximum are just random ninjas that appear after said 3. If this increases anymore and still holds true I will keep updated.
2) The missions are indeed only at multiples of 5. The first mission always gives 5 of said ninja frag, 5 coupons and a varying small reward, in that order. The second mission gives 5 ninja frags, 10 coupons and 5 seal fragments, from the two I have done. (Although this may not be entirely accurate since it was Naruto and Sasuke who, I would imagine, have very similar reward paths.) I have yet to get a ninja to bond level 15 but I would assume the rewards continue to increase. I am interested if we start to see upgraded versions of their frags, hence me working on Naruto, or more in general but that will come later if not here already, I suppose.
3) Shop refreshes are limited to 3 a day as well, despite the Sennin page increasing it with level. This post was last edited by Rozuka at 2017-4-1 06:49