|Mio and Ritsu are childhood friends, but the latter could not remember how they first met. Their first 'serious' interaction came when Ritsu invited Mio to her home and trained her how to be confident and stand up for her shyness. Ritsu encouraged Mio into imagining an audience as pineapples and read out her essay in front of the school audience when they were still in elementary school. Ever since they were kids, Ritsu really loved to tease and scare Mio, especially with horror stories and gross things like barnacles. However, the end result is always a fresh new bump on the drummer's head. Ritsu was first amused over Mio's silky black hair and Mio being a left-handed.
Ritsu also clings onto Mio like a lifeline when it comes to studies, and claims that Mio is the best tutor she has ever met. There have been times when Mio clings onto Ritsu instead; when Mio was being bullied by Sawako or other people, Mio would come running to Ritsu hoping she would save her from distress (sometimes however, Ritsu might join in the bullying too). They both have a similar interest in photography, as Ritsu always brings a digital camera and Mio a film camera around. Ritsu was also the one who introduced music to Mio, and encouraged her to learn bass. It was their promise that they would form a band together, as the bassist and the drummer, since they were little.
|Ritsu's first impression of Yui was that she was a clumsy, childish, and useless girl without tempo. But when Yui joined the Light music club, Ritsu stated that she misjudged her. Later they became really good friends since the two are on the same wavelength.
Yui and Ritsu have a lot in common, such as their lazy and laid-back attitudes, reluctance towards learning (or school in general) and their need for fun. They also have a sweet tooth for Tsumugi's treats and are usually the band members who propose a break first. Yui sometimes gets disappointed when she finds out that Ritsu has also a reliable side, like when she does well on her exams or takes care of her drums.
|Ritsu and Mio first met Tsumugi when she originally intended to join the choir club. Mugi later joins Light Music Club only after witnessing the "fun and painful interaction" between the duo. Ritsu had been polite to Mugi all along, exept once when Mugi suggested that if Ritsu was male, she would be really popular among girls. It was the one and only time Ritsu hit Mugi on the head and shouted at her.
Mugi treasured her friendship with Ritsu very much as seen that she always enjoyed Ritsu's company. Being as observant and wise, Ritsu had brought Mugi to commoners' places like tuck shops and the arcade, as she knows that Mugi might not have visited those places before.
|Other than Yui, Ritsu is can be considered Azusa's next closest senpai (probably because of Ritsu's friendly nature as well). Whenever Azusa had to laugh about Ritsu or nags about the Light music club, Ritsu pull her into a chokehold as punishment (which happened more often in the manga than in the anime).
Azusa badmouthed once about Ritsu being a "lazy and irresponsible leader", although the latter does not seem to mind that comment. It was because of that comment that the two of them grew closer and even found out about Mugi's family wealth together. Azusa had praised Ritsu's cooking before, yet in the same episode, Azusa was the one who pointed out Ritsu's father's underwear in the living room.
|Ritsu and Satoshi are close siblings living together. Ritsu, as the older one, often plans activities with her little brother like going to the cinema. Satoshi is more than once troubled by Ritsu's forgetful nature and has to help her out in such situations. Despite lamenting over it, he is still somehow willing to do so. The social life of her sister seems to interest Satoshi, as he is caught at least two times in front of her door when she had visitors (one time however he blows his cover by himself by laughing about his sister playing Juliet in her class' school act). Ritsu still can be angry with him (seen when he laughed about her) and also has some authority over him as the older sister (seen when he asked her if he could go visit a friend).|
|Ritsu often sees Sawako as a feckless teacher and is more than once out of words when Sawako askes herself about her personal life. Despite Sawako being a teacher and is therefore an authority, the two have a easygoing relation. Ritsu was the first to call her "Sawa-chan" and is the member of HTT who is the most bold toward her (forcing her to become the supervisor of the Light Music Club, calling her "idiot" after she yelled at Azusa, dressing her down when she comes with an hangover or trying to swallow a receipt she has to hand out in front of her). Sawako however is able to gain complete authority over Ritsu when she gets angry, and she also scares her a lot by appearing out of nowhere.|
|Nodoka and Ritsu do often not get along due to Ritsu's laziness and her attitude to often forget to hand in forms for festivals and concerts. At first, Ritsu was envious of Nodoka since she saw in her a rival regarding her friendship with Mio. But since Nodoka was willing to shoulder Ritsu's fault (once again forgetting to hand out a form for the school concert) alongside her, Ritsu dropped her prejudices and the two became friends.|
|Ritsu and Ui do get along well. Ui respects Ritsu as a formidable upperclassmen despite her immature nature and is thankful to her for being such a good friend with her sister. Ritsu is always amazed by Ui's housekeeping skills and told Yui more than once that she is envious and "also wants an Ui at home". The two were seen playing videogames together and Ui was literally crushing Ritsu in it, much to the grief of the latter.|
|Ritsu and Maki are friends from middle school. They are still in contact despite attending different schools now, seen when Maki invites Ritsu and her band over to play at a Live House. When the two groups met coincidentally in London, Ritsu was elated to see a familiar face.|
|Ritsu and Ayame got along the moment they first met since both share a similar personality and are also very alike in other sectors like, for example, clothing. Ayame likes Ritsu's outspoken personality, especially towards Akira. The two also share another physical trait, namely their flat chests and constantly need to sheer up the other because of it, especially when Mio and Sachi are around.|
|Ritsu and Megumi became close friends even though the latter was already attending university. Since Ritsu wants to visit the same university, she asked Megumi to lend her important material, which Megumi glady did. The two hang out so often that Mio supposed that Ritsu might have a boyfriend.|
|Ritsu and Jun know each other through Azusa (however Ritsu tends to forget Jun's surname and calls her "Sasaki"). Jun's first thought about Ritsu were that she seems like a "very cool" person. Her point of view was however corrected by Nodoka who scold Ritsu for forgetting to hand out a request form.|