[Used Can]

Whatever happens, I believe vol.7 will be likely the point at which we know where OreShura is heading. With the story as it is now, I don't see the LN going for more than 10 volumes, and even that, I believe would be a bit too much. I see it ending at volume 8 or 9.

Spoiler for "Gospel of Luke:

Chiwa's backstory has been well-known since the beginning. The only thing she was missing was to become more assertive, which she did at the end of volume 4, and has remained like that until now. I think that's one sign that the ending of the LN is around the corner, especially considering Chiwa is one of the two main girls.

As for Hime, I believe the issues she had left were all dealt with in volume 6. As you've said, she pretty much knows she's out of the race. I take this as another sign of the story reaching it's final stages.

Regarding Ai, she never seemed to have any issues to deal with herself, other than being dishonest, but it'd seem that she's managed to deal with that just fine. My guess is, if there's anything else left to develop about her, will probably go to her manga spin-off.

So, that leaves Masuzu as the only heroine who hasn't had her issues solved - and this goes in terms of her personal life and her own feelings. My guess is the volumes to come will probably start dealing with this, considering all her issues have been mentioned before, but never really expanded on and even less dealt with.

I'm sure the climax of the story is around the corner. I can see volume 7 being delivered on a variety of ways. For example, one could be with Masuzu being completely absent during the whole volume, leaving Eita to resolve his own feelings - whether he loves Masuzu, or Chiwa or someone else, or no one in particular, what he wants to do, how focused he wants to be with his studies as opposed to spending some time with his friends, etc... Another setting could involve a highly Masuzu-centric volume in which we get to explore her character and backstory further. It could simply give us her story an issues, leaving the solution to the next volume, or it could give us all of it. I can also see a mixture of both settings, or Eita and Co. deciding to look for Masuzu.

I agree on Chiwa's ending being more likely than ever. Since the end of volume 4 it's been as if Chiwa has kept on developing and gaining many points, whereas Masuzu has been extremely erratic, indecisive, taking steps back, etc... You see how Chiwa seems much more confident, assertive and she even started learning how to cook. Yet Masuzu, on the other hand, has become too paranoid that she even stalked Eita and Chiwa during volume 5, acted very weird during her focus in that volume, was a serious bitch to Hime at the beginning of volume 6 (not out of malice, though, but clearly out of fear and confusion) and kept denying her own feelings, even though Hime spelled things clearly for her, and even Eita came to realise what Masuzu's feelings might be.

That said, the way I see it, these are your typical ending flags in any of these type of romance settings. Masuzu has been relegated to become some kind of underdog. This started since volume 4 with the girls banding together and Saeko not recognising her as Eita's girlfriend. Volume 6 was basically her lowest, to the point she even formally cut ties with Eita. And I believe her development was left as the last one for a reason.

As for Eita, I think it's been shown since the beginning that he cares a lot about Chiwa. She's been a massive support in his life, and the time he's spent with her plus the time he's spent on his studies to eventually cure her is what has allowed him to overcome the abandonment he felt when his parents left him. He's also grown more conscious of her in the last two volumes, mainly due to her confession. However, I still think he sees her as family.
When it comes down to Masuzu, though, he's been extremely nice with a girl who started off a "relationship" with him through blackmail. Sure, it could be his nice-guy-MC genes, but I believe his actions during volume 4 and especially this volume show he might think of her and enjoys her company much more than what he'd admit. For example, the day after (or was it two days later?) he told her to leak the contents of his diary, when Masuzu didn't show up he thought something along the lines he wanted her to show up in front of him and say "Haha... I've leaked your secrets, you're fucked." or something along those lines, which he immediately though he didn't want her to actually have done that, but simply show him her usual spirit. He also frantically tried to look for her, when the people who saw him on the streets told him he looked like shit. So, romantically or not, he's come to care about Masuzu a great deal.

Personally, I think these are clear flags for a Masuzu end. Both Masuzu and Eita are the only ones left to come clean about their feelings. Masuzu has been on a downward-spiral and her development is yet to come, but likely to come soon. So, whilst I wouldn't write Chiwa out - any twist could happen - I think we might already be on track for a Masuzu end. That said, I can also see an implied end or a no-end, but I'd rather overlook that possibility.