The people here screaming "NTR!", "NTR!", have just reached the right conclusion from the most wrongful premises.
Those users failed to understand the two main characters of this work, Kyotaro Ichikawa and Anna Yamada, are just 13-14 years old kids who had the luckiest of the lucks by being the first love of each other in a story developed in such a way if feels organically real, logically actual. And Bokuyaba have fans precisely because that love is the expected from two kids with that age: clear, pure, white, still protected from the filthness of the real world. Even people expected to bring such dirt, like Adachi, Moeko or Nanjou are, in different stages, supporting such love. If Norio Sakurai wanted to play safe, she only has to keep the current story until graduation from middle school, then does the time-skip to the marriage and that's all. In such case, we could very well be in the last chapters.
But the current environment of the work doesn't appear to suggest we are on that stage. However, if that clear, pure love is expected to be continued by Norio alongside high school, then me, as many others, will begin to question about how much actual or real is that two teenagers, with 16-18 years, keep that love at distance (since both are going to different schools) while many girls and boys are going to be interfering. What's more: it's also expected the lovey-dovey phase Anna and Kyotaro have right now is meant to end at some point and cracks appear where Kyotaro will see things in Anna he doesn't like and viceversa, cracks that could be leveraged by those male or female pretendents of both characters. So, while to talk about NTR is totally inappropiated, almost stupid (Most NTR I've read starts with the premise of the girl being raped and then blackmailed into more rape by a guy while the cuckold is totally not aware about that, so I think it would be a fatal mistake for Norio to enter in that stage), moments like innuendos, insinuations, provocations, jealousness, cheating, infideliting and even break ups are to be totally expected and we are still to see what's the mastership Norio Sakurai will have regarding these. In other words, we have to see how Norio develops that relationship once the protection against real life's filthness is gone by graduating from middle school.
Of course, that means a lot of drama and, if I have followed this forum well, people here is totally allergic to long dramas, so droppings are gonna happen, either because people still wants to see lovey-dovey, fluffiness romance and comedy or because people are not gonna buy that fluffiness in teens or even young adults. It's clearly a dilemma for the author. In my personal preference (in my own experience, it almost sure it's not gonna happen), if given a point where Kyotaro and Anna will be totally unable to cope as a couple, they'll revert as best friends and the story will become more about the affairs and disventures of both with other boyfriends/girlfriends (with the focus in Kyotaro, obviously) before rekindle as lovers once both become proper, successful adults.
Nevertheless, the big picture here is that, if Norio Sakurai wants to keep Bokuyaba as actual, as it's currently happening, it would be totally erroneous for her to think the relationship between Kyotaro and Anna can continue in its fluffy lovey phase disregarding age.