Bloom Into You is a seinen yuri manga by Nakatani Nio that sells itself on the romantic relationship between Nanami Touko and Koito Yuu, as well as their subsequent character developments as a result of their relationship. Ironically, their relationship plays into the same problematic tropes as many pop culture romances. Interestingly, Bloom Into You also explores other relationships outside the main pairing. One of those is Saeki Sayaka’s relationships with a few key people in her life, including Touko, who has been her main love interest for the entirety of her high school life.
Romance, however, is not the only relationship type Bloom Into You spotlights. Two other relationships that are explored are Maki Seiji’s relationships with Koito Yuu and Doujima Suguru. As the aro ace character of Bloom Into You, Maki knows he is incapable of experiencing romantic love. He also doesn’t experience sexual attraction toward others, as the summer camp with the student council quickly shows. Despite Maki not being interested in sex or romance, he still values relationships and manages to establish close friendships with Yuu and Doujima.
Within the Bloom Into You storyline, Maki is a first-year high school student who is also a member of the student council, alongside Doujima and Yuu. Between his two classmates who are likewise underclassmen, Maki spends the most time with Doujima since he is the only other male member of the student council. While Doujima is very much heterosexual and tends to hit on the female members of the student council -- all of whom are actually queer -- he does value Maki's friendship.
Despite being oblivious to Maki's romantic and sexual leanings, Doujima still confides his thoughts about women to Maki, who is a lot more perceptive than his heterosexual friend. Maki occasionally reminds Doujima that not every boy is like him by jokingly alluding to his own asexuality, and he does point out it's not okay to disrespect girls' personal boundaries, not even only "in jest." However, while Doujima is Maki's closest friend within the student council, he has more meaningful interactions with Yuu. Whereas Doujima is preoccupied with wanting to get a girlfriend -- something Maki himself is not interested in -- Yuu is the friend who values his insight on relationships.
Over the course of Yuu's storyline, she becomes preoccupied with Touko, the student council president. Though Yuu strongly believes she is incapable of falling in love just like Maki, the latter knows his own kind and especially knows the difference between being in denial and being genuinely uninterested in romance. Since Maki is very observant of the behavior of those around him, he knows that Yuu is actually conflicted about her feelings for Touko. Regardless of the situation or circumstances, Yuu's feelings for Touko range from genuine concern for her well-being to wanting to take an active role in helping her improve her mental health, finding her maladaptive behavior frustrating to deal with.
One thing Maki consistently observes about Yuu is that her denial of her feelings toward Touko manifests whenever she has a fight or a problem with the latter. Earlier on in the story, whenever Yuu wanted to avoid Touko's company, she would always seek out Maki instead. Whenever Maki caught onto this, he would excuse himself from the situation to force Yuu to deal with her problems with Touko head-on instead of using him as an excuse to avoid her. Maki's insight becomes even more important to Yuu after she confesses her feelings to Touko and misinterprets the latter's apology as a rejection.
In response to having her feelings hurt, Yuu tries to convince herself that she's also aro ace, but Maki knows this isn’t the case. If Yuu was truly aro ace, she would've put firm boundaries between Touko and herself very early on in their relationship and would not have caved into Touko's sexual advances. The fact that Yuu didn’t establish boundaries right away -- nor consistently for that matter -- indicates to Maki that Yuu does feel romantic attraction towards Touko but wants to hold on to her own self-myth. Rather than take Yuu's self-mythologizing at face value, Maki bluntly tells her to stop pretending to be something she's not as a way of masking how she really feels.
During an outing together, Maki challenges Yuu's flawed logic and puts her in a position to be honest with herself about how she truly feels about Touko, and to take action accordingly. What's interesting about the way Maki challenges Yuu is that he doesn't seek to change her the way she attempts to change Touko. Instead, he encourages her to take ownership of her feelings and to be authentic. While Maki's behavior may come off as a bit callous, he's being the friend Yuu needs: the one who encourages her to not run away from her problems like Touko does and to openly communicate the way a mature person would. Maki also fulfills this role for Yuu without playing into the potential love interest trope, thus cementing their relationship as aromantic.