This was also one of my 1st guesses for the ending during the discussions on 129, if i remember correctly. It's very realistic ending, and to be honest, the one i want the most currently.
Yeah, it's the one I want most right now.
IF Shinobu does end up dating Fumi, the only way I can see it ending is if, aside from NTR bullshit, Fumi willingly lets him go to pursue Sakura.
Aside from that? Even if the window was there, I don't think it'd fit for Shinobu's character to just ditch Fumi for Sakura or leave her.
Sakura and Fumi got along when they met. Fumi apologized as she felt at fault for what happened between Shinobu and Sakura. Honestly? Respect. She's honest about it.
That's why if they stay together, I can see Fumi insisting that they support Sakura together while also focusing on their own ambitions. She'd know Shinobu would want to. Sakura ends up not alone as she has honest friends by her side (after her character growth that could happen) and they move on side by side.
Fumi is happy with Shinobu.
Sakura gets her redemption and is able to walk beside them on this path together.