Sakaki beloved to the point of Even the Girls Want Her, in one instance having an enormous mixed-gender crowd following her trying to get her to join their clubs, and she's frustrated by the groups of female classmates continually squeeing over how cool she is (not because they're girls, but because she wants to be cute instead of cool). As for specific characters:
Kaori's borderline Stalker with a Crush behavior towards Sakaki is hilariously obvious, only remaining subtext because it's never explicitly stated, including things like constantly blushing around her and complementing her, her desperation for them to be in the same class, and her supreme jealousy at any of the other girls getting close to her. The most blatant example is either her absolute joy at getting to dance with Sakaki at the end of the first Sports Festival (with an Imagine Spot depicting the most G-rated orgasm ever, complete with a field of flowers and a group of jets trailing rainbow colours), or hyperventilating at seeing a picture of Sakaki in a bikini (followed by her becoming nearly apoplectic at a picture of Tomo sleeping next to Sakaki).
Kagura's bizarre obsession with becoming Sakaki's "rival", alternating between trying to get closer to Sakaki and trying to crush her in any sort of competition, is dripping with unrequited crush vibes. Kaori sees what's happening right away, lurking in the background of their first meeting. For her part Sakaki barely acknowledges her, which only seems to make Kagura more determined to be noticed.
Chiyo seems to develop a sweet little Precocious Crush on Sakaki, looking up to her figuratively and literally, repeatedly inviting her on group outings, marveling at her size and her breasts, and generally gravitating towards her when she wants someone to be around. Fortunately, Sakaki seems content in the Cool Big Sis role.
Minamo and Yukari are Heterosexual Life-Partners at the very least, one rarely seen without the other unless they're at work, closely involved in each others' personal and professional lives with a relationship that stretches back over a decade. Despite Minamo's constant frustration with Yukari's antics and the trouble she causes, she's always willing to help Yukari and shows no sign of ending the relationship, and for all Yukari's bluster it's clear she cares for Minamo in turn.
Yomi and Tomo are almost a younger version of Minamo and Yukari, complete with similar personalities and the same Odd Couple dynamics. When told that the older pair have been together since high school, Tomo proudly boasts that she and Yomi have been together since grade school. And the 10th anniversary chapters give us this◊, only barely out-of-context.
In general, Tomo seems obsessed with boob sizes to the point where it shows less about her jealousy and more about just how long she spends staring at the other girls' breasts.
Osaka develops a weird obsession with Chiyo, the latter repeatedly showing up in her dreams and having the most Imagine Spots about her, and develops the same overprotective instincts towards her that Sakaki does (which results in a funny scene where Osaka rushes to save Chiyo from danger, complete with dramatically shouting her name and running in slow motion, only for Sakaki to casually help her while Osaka struggles to get past Yomi).