Spoiler Warning: This article contains major spoilers regarding the future plot lines of Tonikawa original manga that is yet be animated. Read at your own risk.
Chitose and Tsukasa are not sisters and they are not related by blood. The two spent some time together in the household of Tokiko Tsukuyomi who acted as both of their guardians. Due to them living under the same roof, Chitose has grown an attachment to Tsukasa. As a sister, Chitose loves and wants to protect her older sister no matter what resulting in her developing a bit of a sister complex.

Chitose Kaginoji first made an appearance in episode four of season one of TONIKAWA: Over the Moon for You. At first glance, Chitose appears to be a cute but very outspoken lady who doesn’t even think twice when she speaks. Chitose had conveyed the moment she had met Nasa Yuzaki of her disapproval of their marriage. This is due to her deep love for her sister-like family who basically guided her as she grows up.
The relationship that Chitose Kaginoji and Tsukasa Yuzaki have can be traced back to her great-grandmother, Tokiko Tsukuyomi. Tokiko Tsukuyomi is considered to be Tsukasa’s friend ever since. She had been by Tsukasa’s side for a long time and did not leave her even when she got old. Tokiko took the responsibility to take care of her friend and bought land just for her. This is where Tsukasa will meet her soon-to-be spoiled but annoyingly cute younger sister.
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How Did Tsukasa and Chitose Become Sisters?
Tsukasa doesn’t necessarily treat Chitose as her sister for one main reason. She sees Chitose as how Tokiko Tsukuyomi sees her granddaughter. However, the age gap between her great-grandmother and Tsukasa made Chitose treat her as if she was her older sister.

Tokiko Tsukuyomi owned a very large land. Due to Tokiko’s determination to make her friend, Tsukasa’s, dream come true, she had to work and study hard. And when Tokiko finally achieved something and became successful, she purchases a huge land for her friend and her own family to live in. In the original manga, Chitose told that her grandmother always prevented her to visit the house located at the top of the mountain. Tokiko told her great-granddaughter that it was only her who is allowed to do that.

But, the young girl knew better. As sneaky as she is now, she didn’t hesitate to disobey her grandmother out of curiosity. Tsukasa Yuzaki was a shut-in who literally never gets out of the house and just spends most of her time reading the mangas her friend gives her. The house and Tsukasa living there became the little secret of Tsukasa and Tokiko.
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With the thought of the house being abandoned, she tried to sneak but saw something that scared her. In the house, she saw a scary but beautiful woman, Tsukasa Tsukuyomi. She ran as fast as she can from the house but ended up falling into a cliff. However, Tsukasa comes in and was just in time to save her from falling. For Chitose, it was a near-death experience which is why she is extremely grateful to Tsukasa.

From then, she grew fond of her and decided to spend most of her time in Tsukasa’s household together with her grandmother. Not long after their first meeting, Tsukasa ended up living in Tokiko’s household because of the outspoken Chitose. She pointed out to Tsukasa that being a shut-in will not do her any good. Chitose told Tsukasa that it is better for her to live with them in her great-grandmother’s house which Tokiko fully agreed to.
Does Chitose Know that Tsukasa is Married?
Yes, she does and she is completely against them being married. When the little sister of Tsukasa arrived in episode four of season one, she instantly expressed her disapproval of Nasa Yuzaki. Chitose appears to be the only granddaughter of Tokiko. Hence, it is quite understandable why she acts the way she is.
Chitose can be described as a rich spoiled brat whose demands are always followed by her two maids, Charlotte and Aurora. She has a sort of sister complex due to her affection for Tsukasa. Chitose even went to Nasa’s place and told that it should be her whom her sister should marry. This doesn’t mean anything beyond their sister relationship. She just simply adores her sister so much and idolizes her that is why the thought of her being married made her furious.

Chitose is not that bad of a person. When she didn’t know that Nasa Yuzaki was Tsukasa’s husband she was kind to him and was very respectful. But, everything changed when she found out about the relationship between the two. Chitose took Nasa into their mansion using her limousine hoping to make a scandal that would drive Tsukasa to divorce his husband. However, this didn’t work for Tsukasa because she saw through the photoshopped that Chitose did with the photos and she trusts her husband.
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Moreover, you would think that Chitose would end her goal to separate them after failing once but she didn’t. When Tsukasa and Nasa traveled to meet Nasa’s parents, Chitose decided to follow them together with Charlotte and Aurora. She wanted to make the slightest trouble during their trip that would make Tsukasa and Nasa fight with each other leading to their divorce. However, instead of fighting the two just ends up firing which infuriated Chitose pushing her to confront Tsukasa.

She expressed her disappointment towards her sister who was acting all lovey-dovey with her husband like a normal girl. This proves that marriage is not all about the two people who got married. Marriage also means forming a commitment to the family of your partner. Therefore, Nasa was determined to change Chitose’s perspective by spending some time with her strolling around a city.
How Did Nasa Got Chitose’s Approval?
Nasa finally gained a little bit of Chitose’s approval after their date. Yes, the two went on a date but only to convince Chitose that Nasa is a good man who would never treat her sister badly. Chitose, Charlotte, and Aurora followed the couple all the way to Kyoto to ruin every chance of them flirting.

Instead of spending his time in Kyoto with his wife, Nasa decided to take Chitose hoping that he can finally gain her approval. Nasa wishes that more people will be happy about their marriage, including Tsukasa’s sister-like family. Charlotte and Aurora were fully on board with the plan; hence, they convinced Tsukasa to go with them.
During their stroll around Kyoto, Nasa wishes to talk to Chitose more. However, Chitose had better plans and that is to assess Nasa by her acting as his girlfriend for the day. What Chitose didn’t know is that Nasa Yuzaki is a man who always prepares before any battle. Nasa had a detailed Kyoto strategy guide with him that tells about the tourist spots in Kyoto and the delicious food they can try.

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Chitose always emphasizes to Nasa that she doesn’t know anything about her which he didn’t even try to deny. Thus, she keeps on questioning why Tsukasa chose to marry him. However, what will break the gap between these two is the love and admiration they have for Tsukasa. Nasa explained to Chitose that he considers himself lucky for meeting Tsukasa on the day of the accident.
I know that I don’t know her as well as you do, but I intend to spend my entire life proving our love is real. You don’t get married because you’ve proven you’re in love. You get married so that you can prove it.
Nasa Yuzaki to Chitose Kaginoji (Season 2: Episode 7)
These words of Nasa may have not gained a hundred percent of Chitose’s approval. But, it was enough for her to go back to Tokyo and let the lovebirds go on with their trip to Nasa’s parents. The marriage of Nasa and Yuzaki did not only affected their lives but also the people around them.

Chitose may still be adjusting to her sister being away from her. She is not a bad sister for feeling the way she feels. She knows that her sister loves Nasa and that Nasa loves her sister deeply too. Gaining her approval is a step-by-step process, besides she even attended the Takoyaki Party hosted by the lovers. Chitose just needs a bit more time to digest the changes around her and we hope that in season two she will finally give the lovers a thumbs up.