OK so, I don't know why I'm even doing this considering pretty much everyone already agrees that this series is gay as fuck, but screw it, I'm going through each chapter and pointing out how fucking absolutely on purpose all the gay stuff is. I'm gonna call senpai by her surname Honami because both of them having K names just inevitably makes me fuck up.
Chapter 1 --
The whole story opens with girls meets girl. The whole "moving to a new town" thing comes later, but the story really wants you to know this is about these two girls from page 1.
Also she's opening with "Do you like Salamanders?" which as will come up later, isn't really how she normally deals with the public. She's starting with an icebreaker, trying to start a conversation with this random girl. Konatsu, meanwhile, is all like, "A pretty girl is talking to me!!!" It's not quite as gay as Kumiko from Euphonium's, "Crap, a pretty girl!", but still, she seems pretty amazed. There's just so much immediate romantic tension here, with Honami inviting her to come back and Konatsu looking all nervous and intrigued by the invitation (and not because she's super into aquariums!).
Page 16, and hey, it's our first mention of the summer festival already! Specifically, a boy asked Honami out to the festival and got turned down. Konatsu thinks that Honami's pretty popular. The teacher yells at Konatsu to not just stare out into space on her first day, but we already saw on the previous page what she's really staring at - Honami outside in PE.
Their whole second meeting is pretty romantic, too. It's also sorta interesting that they immediately go to first names, which is relatively intimate, especially when one is older. It feels like part of this manga's reversal of Class-S tropes - Konatsu meets this impossibly cool, pretty senpai... And instead of having that very Class-S kouhai-senpai relationship, instead they go straight to an equal relationship, and she realizes that Honami's actually a pretty big dork. The author's purposefully referencing, and then subverting, some of those standard romantic friendship / gay subtext tropes.
What's really interesting is on page 35. Her dad messages her asking if she's made any new friends, and Konatsu's like, "Should I tell him the truth?" Next panel is her thinking of Honami's face, third panel is Konatsu blushing. She tells her dad that she made one friend, and then is like, "I'm not lying..." before wondering if it would be OK for her to visit Honami tomorrow, and trying to think of an excuse to do so, and feeling all embarrassed about it.
So like, does any of that sequence really make a lick of sense if all she's thinking about is how she wants to be friends? It really doesn't. The "I'm not lying" is pretty obviously meant to be followed by, "But I'm not telling the whole truth about her, either." And it's not because she's feeling a bit lonely, because as the not-a-lizard tells her in a couple pages, if she's lonely she could just go try to hang out with her classmates. But she's not hanging out with her classmates, she's in the library researching Salamanders, trying to figure out a name to submit, all so she'll have an excuse to go back to visit Honami. She asks herself, "Why am I so hung up on this?"
When she finally goes to the aquarium club itself, she sees two boys inside. Boys are useful props in yuri, because when they say that they like a girl there's no doubt about how they mean it. And in this case the boys are very useful props indeed. "If you like Honami, just join the club already. There aren't any other members, so you'd have her all to yourself." Again, the author's setting a boy's romantic feelings for Honami right next to Konatsu's (as yet unrevealed, technically) feelings for Honami. If the author wanted this to just be a story about Girl's Friendship she could've had it be a couple of girls talking about how cool senpai is, but nope, it's boys talking about liking a girl and Konatsu relating to that. If she wanted romantic friendship she could've just made this a girl's school, or at least done that thing where boys never really show up on screen. Yes it's subtext, more or less, but this ain't an accident, the author is doing this on purpose.
Meanwhile Honami is totally wondering about Konatsu, before resolving "I'll just do my club duties before thinking about anything weird." Honami feels like her thoughts about Konatsu are weird, not normal.
Notice the lack of honorifics when Konatsu is naming the salamander after Honami's first name, Koyuki. First name, no honorifics is a very intimate form of address, and she's going, "It's lonely without you, Koyuki!!" No wonder Honami freaks out with the second-hand kiss. The whole scene is them sort of teasing intimacy - not quite no-honorifics, not exactly a real kiss but thinking of one... This sort of experimental pushing of boundaries shows up regularly in later chapters, in a way that is not at all about gals being pals, but is very much like having a first girlfriend.
Heh, that was a lot longer than I had planned for only one chapter. But like, jesus christ it's so gay! I see a lot of folks in the comments acting like something is either gay, or "just" subtext, and like... Yeah, the manga never quiiiite outright tells you what it's doing, but that doesn't mean it isn't still gay as fuck. It's just subtly written.