|⚠️|| Spoiler Warning!
|Other names|| Dera-chan
Onee-chan (Used by Haru Onodera)
|Age|| 15 (1st Year Arc) |
16 (2nd Year Arc)
17 (3rd Year Arc)
|Date of birth|| June 15th
|Occupation||Student (formerly), Worker at their Family Sweets Shop, Baker|
|Goal||To confess to Raku Ichijō (Accomplished; Rejected)|
|Likes|| Raku Ichijō (Formerly);
Animals; Pastry designing
|Quote||"Don't let go no matter what, okay?"|
|Image gallery (0)|
Kosaki Miyanagi née Onodera (小野寺 小咲, Onodera Kosaki) is one of the main characters of the Nisekoi series. She is one of the love interest of Raku Ichijō.
Kosaki comes from a family of pastry chefs; all of whom specialize in making and decorating candies. However, her father is missing for the most part of the series and is hinted to have his own work to deal with. Thus, Kosaki has since been living with her eccentric mother and her feisty younger sister in their Japanese candy shop. Ironically, despite this environment, she grows up to be very timid by nature.
At one point during her childhood, Kosaki became acquainted with Raku Ichijō, Chitoge Kirisaki, Marika Tachibana, Yui Kanakura and Seishirō Tsugumi. They soon grew to be close friends with Raku in particular, whom she was in love with. In the day of their parting, the group proposes to give each other several keys and a locket (belonging to Raku) as a testament to their promise to meet again in the future, with the owner of the true key capable of unlocking the locket be the person Raku would marry. Kosaki would eventually receive the true key from Chitoge - whom Raku originally intended to be its recipient - after the latter overheard that the two are mutually in love and seeing their lover's mark carved on a rock. As such, Raku and Kosaki declared to each other their promise of marriage for the future.
As the memories of their childhood soon fade away, Kosaki has also gone to the same middle school as Ruri Miyamoto (Kosaki's best friend) and Raku.
Kosaki is discreet, innocent, and slightly timid. She is very kind, taking care of Raku Ichijō when he is wounded or ill. Generally, she opts to think carefully before acting, as seen when she stalls her confession to Raku in consideration that he may have feelings for Chitoge Kirisaki.
At times, Kosaki shows signs of lacking self-confidence and often needs the support of Ruri Miyamoto (Kosaki's best friend). This is also proven by the fact that Kosaki's younger sister is very over-protective of her (even though Kosaki is older than Haru). In confrontations with Raku, Kosaki initially needs encouragement from Ruri to attempt any form of contact as she lacks self-confidence around him.
Kosaki works well with her classmates, possessing close friends and being the most popular girl for the boys before Chitoge transferred and after Chitoge and Raku allegedly began dating.
As the series progresses Kosaki takes strides into overcoming her timidness and instead try to be more upfront with her feelings, especially in regards to finally confessing her love to Raku. But while Kosaki retains most of her personality quirks, she has more or less matured into a strong and caring woman.
Main Article: Relationships of Kosaki Onodera
Kosaki is a fair-skinned teenage girl with dark brown, shoulder-length hair with one long strand of hair which she keeps combed neatly to the left side of her face and chocolate brown eyes. Kosaki is average in height and has a thin figure. She looks a lot like her mother.
She has the school uniform as most of her classmates do which is a half-sleeved or long-sleeved (depending on the season) white shirt with a blue sailor-style collar attached at the lower part of her neck that connects a thin orange tie that is laced through a loop at the end of the shirt, making a little part of the tie to reach the skirt. The skirt reaches around the upper thighs and is a blue-colored fabric that is accompanied by her white knee-length socks and brown slip-on shoes.
Kosaki's swimming attire consists of bikinis that are usually pink and/or frilly, but for a swim meet, Kosaki wore the school's navy blue swimsuit. When she works at her family's sweets shop, she wears her uniform which consists of a light navy blue v-neck dress with short sleeves that have a small red trim on the end. The collar of the dress also has the same small red trimming. She wears a small round hat, a long white apron that reaches the end of her dress and light black stockings.
- Natural Affinity for Animals:
Kosaki Onodera is extremely popular around the animals she takes care of. This is seen with the school pets and also with Marika's parrot named 'Raku Dearest'
- Genius Taster:
In contrast to her inability to cook food, Kosaki - as noted by Haru - has sensitive taste buds, and thus is greatly suited to be a taster. Kosaki is always specific in describing the flavour of the food she is tasting. She is so good that it is one of the ways she helps out with her mother's business.
- Talented Decorator
Kosaki proved her worth in the kitchen by being a very talented food decorator. This is the reason why all her cooking looks scrumptious but turn out inedible to the extreme. This skill also extends to other activities such as building sand castles at the beach.
Kosaki's proud of this talent of hers but during her career counselling, she's not decided on what she'll be doing with her future. However, it is seen that she finally does become a baker, a profession which requires decoration over all things else best suited to her.
During the majority of Nisekoi, Kosaki was shown as a terrible cook, be that sweets, chocolate, or meal, to the point that everyone eating her cooking will be incapacitated shortly. However, once in ten-thousand attempts she can produce miraculous dish that tastes delicious (the valentine chocolate cake for Raku). She also becomes a good cook when she is depressed.
In the epilogue, it is shown that when Raku contacted Kosaki to check up on the wedding cake prototype, she was working alone with many ingredients surrounding her, suggesting that her cooking abilities has improved considerably.
- The name Kosaki means "small, little" (小) (ko) and "blossom" (咲) (saki).
- Kosaki's surname Onodera means "small" (小) (o), "field, wilderness" (野) (no) and "temple" (寺) (dera).
- Although Kosaki is very talented in decorating cakes, she is known to be a terrible cook. Strangely, when she is depressed the outcome of her cooking is reversed.
- Kosaki befriended Ruri Miyamoto in a ball game tournament as first-year students.
- Kosaki has a picture book from the past that holds clues as to who the "promise girl" really is. It was a gift from Chitoge Kirisaki as a 'symbol of their friendship'.
- The name of Kosaki's candy shop is called Japanese Candies "Onodera".
- Kosaki loves sculpting and is shown to be extremely talented with it; on a trip to the beach with Raku Ichijō & co., she effortlessly sculpts buildings and statues out of the sand.
- Kosaki's favorite food is candied sweet potatoes  and her least favorite is konnyaku. She not only dislikes konnyaku, but she is actually afraid of it.
- Kosaki's favorite colors are white and red.
- Kosaki is currently the most popular character, based on the results of all three popularity polls.
- Kosaki is also the main protagonist in Nisekoi's spin-off manga, Magical Pâtissier Kosaki-chan.
- Kosaki is the holder of the 'true' key said to be able to unlock Raku's pendant, signifying her as the 'promised girl'.
- Despite the fact that Kosaki was indeed Raku's first love, she would not have been able to become Raku's 'promised girl' had it not been for Chitoge giving up the 'true' key to her.
- Additionally, this fact did not help Kosaki win Raku's heart in the end but it did tear the latter apart with indecision until he made a firm resolve to choose Chitoge.
- While visiting the beach, Kosaki is seen building a sand castle that's an allusion to the 'Attack on Titan' series.
- Kosaki is shown to have a daughter named Sasa Miyanagi in the bonus/omake chapter. The identity of "Miyanagi-san" (the husband of Kosaki) has been speculated by fans for long, which indicates that Kosaki is now Kosaki Miyanagi. Some theories suggest that he is the widower who Marika Tachibana is briefly engaged to in the series. However, none of the theories are backed with consistent logic or canon revelations yet.
- Kana Hanazawa (Kosaki's voice actress) has coincidentally also voiced characters with the same names and surnames like Ruri Miyamoto (Ruri Gokou from Oreimo) and Marika Tachibana (Kanade Tachibana from Angel Beats!).