I was waiting in the dentist's office for my appointment and thinking about bllk (as you do), mainly about Isagi's arc trajectory which led me to thinking about his ships etc and why bachisagi are the true soulmates of this manga— ehem. So then I ended up making this on my phone to illustrate my thoughts:
Every major arc/event goes through a cycle of: introduce new rival, new rival has an alternate relationship path, mild NTR via rivalry with Isagi, resolution reached with Isagi's win. Other characters make guest appearances, for example Hiori in NEL. U20 also relevant because while they're siblings (and I'm not trying to imply anything romantic here, that is up to you to consider--) Sae and Rin essentially play out the same pattern with Rin notably becoming most competitive with Isagi after this due to Sae's recognition of Isagi (and lack thereof towards Rin). The pattern was broken thanks to Loki's badass self-confidence lmao.
Bunny and Sae are pending; in the group art of the NG11 it's Sae looking with determination/resentment at him without acknowledgement on Bunny's end which is interesting because it's paralleling the Rin -> Sae -> Isagi situation in the U20 arc.
I'm interested in Bachira's emotional through line with Isagi cause like I mentioned their relationship is the most enduring aspect of Isagi's arc so far. We'll see...











