Osana Najimi

Osana Najimi is a planned  ''' first rival for Senpai's affections. She will be used as a tutorial at the beginning of the game. She is a student at Akademi High. '''

Since her programming is still incomplete, Osana Najimi cannot be interacted with (include killing, talking, etc.). Yet, she'll still confess her feelings to Senpai on Friday, resulting in the "Heartbroken" scene. During gameplay, you can find her standing underneath the first cherry blossom tree on the left row, close to the School Gates.

She is not active yet because YandereDev wants to give a different character model to make her more unique, but her character model is not compatible with all of the animators that were made for the other female skeleton that the rest of the female have. Osana can't be put into the game unless a character rigger makes a control rig for her, and an animator uses this rig to create a full set of animations for her, or YandereDev gives her the same character model and animation as all of the other female students.

The downside of giving her the same character model as all the other female students is that she will look like a clone of Yandere-chan, but with different eyes, hair, and stockings. So far, YandereDev can't find anyone to get it done. It may be a while until she is implemented without a whole bunch of Osana-specific "event" animations as well.

YandereDev also has mixed feelings about Osana. Her current design is super cute, and does not suit his opinion of tsundere characters. To balance this problem, he would either choose a personality that suits her cutest appearance, change her design so that it suits her tsundere status, or split her up into two sisters, a childhood friend and a tsundere childhood friend. He doesn't like the latter deal too much because the death of one sister might affect the other so strongly that she couldn't consider dating.

Appearance
Osana Najimi is an extremely short girl and is actually the shortest character in the game. She has ruddy cheeks in a blush, a soft smile, orange eyes, and pale skin. Her ginger hair is worn in two slightly curling pigtails. To keep her hair up, she wears ruffled pink and white polka-dotted scrunchies and a purple ribbon. She wears the default female school uniform unless customized, and black shoes, although with white Kogal-style leg warmers.

She is probably getting an update with long twin tails, the same pink scrunchies with white polka dots, and salmon socks with white polka dots. This has not been confirmed but it is quite possible as the developer mentioned that her appearance is somewhat inconsistent with her personality. This character was also in a small cameo in one of YandereDev's videos, "I Want My Senpai Back" The tsundere was later killed off in the video.

Scenes
In the original intro to the game when you run into Senpai, she can be seen talking to Senpai and acting like a tsundere towards him.

You can see that intro on YandereDev's YouTube channel. She also appears in the spin-off game Yandere Clicker. Her face was used for the "Imouto" option, described as "A kawaii Imouto who will stab Senpai for you". However, she is not Senpai's little sister and should not be mistaken as such.

In the April 3rd, 2015 build, the photographs folder had a lot of pictures of her in different positions. You cannot see her move from her spot in the actual game. However, in the (Date Needed) Update, you can press the space bar to see her cycle through seven different animations.

In the second intro added in the August 15th, 2015 build, Osana is mentioned by Info-chan as she requests that Yandere-chan murder the girl. Info-chan expresses that she wants Yandere-chan to "make her suffer". It is unknown what Info-chan has against Osana.

Personality
Osana Najimi was originally tsundere, which is a person that is very sweet, kind, and cute, but projects a hostile attitude to those around her, often only towards their love interest. It's not very likely that Senpai would know about her crush on him, as she repeatedly insults him and seems oblivious. Kokona, a test rival, indeed does lament how Senpai never notices her feelings. Regardless of Osana's rudeness and Senpai's ignorance, Osana is still very considerate. In the original intro, she is shown walking Senpai to school.

The characterization might have changed. On this page at the very bottom, YandereDev says that Osana Najimi is the tsundere childhood best friend of Senpai. The page was right about The Nurse, as confirmed on The Nurse's page which would suggest that some of the info might still be true, despite the fact that the page was extremely ancient. Yet even so, on the Rivals page, in the Trivia section you will notice that the page might've been wrong about the Imouto, another rival, being innocent and sweet. Therefore, because there was a change to the Imouto's personality, the same could've been done to Osana. This is even more implied by the second intro, which shows nothing about what Osana is really like. The only thing we know now is that Osana likes Senpai, is a target of Info-chan and Yandere-chan, and believes in the myth about the cherry tree behind the school.

However, unlike the Imouto, Osana has no real known reason for her character to change. The Imouto changed so that you wouldn't feel too bad about killing her because she's already kind of immoral for being lewd instead of pure as her original personality was. Osana seems to have no reason like that so there's a chance she's still the same.

When you scroll through her animations she looks a bit girly with the way she poses, suggesting that she has quite the feminine side.

She may not be a good friend, considering that if you get rid of her non-lethally and Senpai's sister dies, she will not go back and care for Senpai.

Senpai
They were childhood friends in the first intro. Osana has a crush on him, although he does not seem to be aware of it. The first opening shows Osana and Senpai together, and even walking to school with each other.

In the second intro on it's own there is no information about what their relationship now is. Osana still has a crush on him though and will still confess to him.

Yandere-chan
Osana Najimi is a target of Yandere-chan because she is a rival to Senpai's affections. In the first intro, Yandere-chan qualms about killing others. She simply wanted a love life and Osana was in the way, but Info-chan, a glory-hungry journalist, convinces Yandere-chan to kill Osana. In the next intro, Yandere-chan already wanted Osana out of the way, by any means necessary. Info-chan just encouraged her more and gave her some info. However, Yandere-chan does not need to kill or hurt Osana in any way, like all the other rivals.

Info-chan
In the first opening Info-chan didn't hold anything truly personal against Osana. Still, it is now known that back then Info-chan was the main antagonist who was going to be a rival for your Senpai, as seen on Info-chan's page. It is also known that in the original intro Info-chan wanted some terrible events to unfold at Akademi High to boost her newspaper sales.

In the second intro it is not stated why Info-chan is going against Osana. Info-chan simply wants Osana to suffer, though anything about being a journalist is never stated.

Trivia

 * Osana Najimi's name is a pun on "osananajimi," a common trope in the romance genre which means "Childhood Friend" in English.
 * In the Challenges menu, there's a sillhouette of a girl victim that seems to resemble Osana's original look.
 * In the video I Want My Senpai Back, Osana is voiced by Brittany Lauda . Her VA also happens to play Audrey from the adult game HuniePop.
 * She is the first official rival to be introduced so far during the build era.
 * She is the first tsundere character to be introduced by YandereDev, the second being Tsundere-chan from Kuudere Simulator.
 * Osana's hair cannot be loaded by any other female NPCS.
 * She makes a small cameo in the April Fools' trailer with her photos appearing on the corkboard.
 * You can buy Osana Najimi's 3D model on the Unity Asset store, and her model is named Satomi Makise.
 * Currently, except the text message intro, Info-chan won't give you information about her due to not recognizing her placeholder model.
 * If you press spacebar, Osana's idle animation will change. She will do different animations.
 * It is implied on Twitter that Osana's birthday will be in January, most likely the 1st.
 * Osana is seemingly unaffected in every mode there currently is.