Celine

Celine was Lala's gift for Rito's 16th birthday. She is sort of a child-like humanoid/plant alien, but originally was a rare multi-story, sentient sunflower kept in the Yuuki residence backyard.

Appearance
Originally, she was an extremely huge sentient sunflower with purple petals around the face, which is just a mouth with sharp teeth, two huge leaves behind her head, she also has vines to be used as hands.

In her human form she resembles a human child with blue eyes and light green hair with a flower on top with light pink petals. In the anime, she only has two long toes on each of her feet. In the manga, her feet appear more like those of human babies.

In the 15th side story of the To LOVE-Ru Darkness, Celine became older with the effect of the moonlight in a full moon. But the effect only last for the night of the full moon.

Personality
Celine's personality is exactly that of a regular toddler. She is often seen to be running around playfully, seems to be quite curious, and likes to play around with machines, Lala's inventions or Momo's plants when she has no idea what they do, which manages to cause a lot of trouble.

As an infant, Celine has a tendency of wanting breast feeding, so she constantly jumps on to other women's breasts and begins sucking them out of instinct. Celine enjoys playing video games, watching Magical Kyouko, gardening and eating ramen. Celine is normally very well behaved, albeit troublesome in her young age, but can become fussy and impatient just like a human toddler when she is held back or comes across events that annoy her, but also seems to have an understanding for discipline and sometimes even seems guilty when she realises what she has done is wrong, as evidenced by her almost always sticking her finger to her mouth and listening when being lectured or scolded. She has a vast appetite, due to Lala experimenting on feeding her different things, and even enjoys eating Yami's taiyaki soup when she makes it.

In her grown up body, she seems more calm and mature but still slightly playful. She refers to Rito and Mikan as her family and desires to be close to them. As an older girl, she is able to converse in the same language as the other characters, but in her usual infant form, she just continually says "Mau", much like a baby.

Plot
In the chapter 27, Lala give Celine to for Rito for his 16th birthday and she start to live in Yuuki residence backyard. Although seemingly monstrous, Rito cares for Celine deeply referring to her as his family.

When Celine seemed to have contracted the Kare Kare disease in chapter 124, Rito was fully dedicated to find the Luck-Berry to save her. With his friends, they journey to the S-level-danger class planet Mistletoe to retrieve the antidote, only to return and find the plant all dried up. They realised that it was germinating and from its single seed, burst out Celine; taking the appearance of an infant girl, with a flower on her head. This event even shocked even Momo, who is very knowledgeable with the galaxy's flora, stating Celine's biological makeup is still a complete mystery to her.

A running gag as a child is Celine will playfully tackle any girl and attempt to suck milk from her breasts, or jump onto someone out of nowhere, most of the time causing a perverted accident. Another running gag it she is often mistaken for being Rito's daughter.

Celine makes guest appearances in the OVA adaptation (as a plant near the end of OVA 4 and as an infant in OVA 6 part 3) of first anime and becomes a regular character with her infant form in Motto To LOVE-Ru.

Powers and Abilities

 * Plant Physiology: In Celine's originally plant form, she was able to move most of her own body at will and control her vines like hands, she also behaves akin to a human; perspiring when the climate is humid, wearing an oversized scarf during a chilly day and eating a bowl of ramen when hungry (though Celine still needs the basic nutrients of water and sunlight). Even in her human form, Celine still retains some plant like feature, such as the flower on her head. Celine's physiology is quite unique and rare among most plant-life that even an expert like Momo is puzzled by her capabilities.
 * Human Transformation: Celine was originally a giant alien sunflower as tall as the Yuuki house. But after a period of germination, Celine abandoned her giant original plant body and emerged as a human-like infant (It is unknown if she will age like one).
 * Pheromone Pollen: Because of the parental love Rito had shown her, whenever she gets drunk (off cola), she playfully walks around spraying pollen out of the flower on her head, causing anyone who breathes in this pollen to grow a tiny flower on their head and temporarily fall in love with Rito (because of Celine's own affections for Rito, the pollen effect has him as the person to fall in love with). The effects wear off after 30–45 minutes or so when the flower falls off of their head and they might have no memory of the events that happened when under the pollen's influence.
 * Age Transformation: When the moon is full at night, Celine transforms into an older version of herself and is even able to speak. When the night has past, she turns back into her infant form.
 * Strength and Stamina: There are vague evidences that she is capable of strength greater than her size and appearance would suggest. Despite her small size, she is capable of jumping really high, able to reach a person's face, or maybe even higher. And while drunk, she is seen running around town almost faster than Rito can keep up.

Yūki Rito
Ever since Lala gave her as a gift to Rito on his 16th birthday, he has been taking good care of her as if she was part of his family, at times being seen watering and even nurturing her. This great deal of care for Celine was shown when he was willing to go up against impossible and dangerous odds to retrieve a cure for her when she was seemingly dying from an illness, which would later be revealed that she was only germinating.

She perceives Rito as her adoptive father because of how he took care of her and because of her child-like appearance and closeness with him, she is often mistaken as his daughter; like the time when Rito's mother thought he was her dad she immediately asked who was the mother. She is one of the few characters with unique traits that causes trouble for him, as whenever she is drunk from being drinking cola, she releases her pollen that instantly makes whoever smells it to be temporarily fall in love with Rito. She loves him deeply, enjoys being with him, and enjoys getting to see him and getting cared for by him, as whenever she sees Rito, she immediately jumps onto him, which mostly catches him by surprise and at times, can also cause Rito to fall and cause him to accidentally fall on to and/or grope any girl near him when she does so.

Momo Belia Deviluke
Celine and Momo share a sisterly bond, communicating and socializing with each other via Momo's inborn ability to speak with plants. Celine is often taught right from wrong by Momo, being told what she isn't allowed to play with or touch after doing so, to which she seemingly understands and feels guilty about. When given the chance, Momo would use Celine's pollen to advance her harem plan.

Yūki Mikan
Mikan and Celine get along really well and they are seen playing together on some occasions. Sometimes Celine would copy Mikan's motherly personality and Mikan was the one who named her. Mikan can act motherly towards Celine, especially after seeing her "all grown up", where she expressed how Celine's baby clothes would never fit her again and would miss seeing her wear them.

Kotegawa Yui
Celine has shown a strong liking for Yui, as pointed out by Rito when Celine hugged her. Yui was once mistaken as being Celine's mother (and consequently Rito's wife) which she greatly objected to. However, this even prompted her to imagine what it would be like if they were to become a family. She then promptly chastised herself for thinking about Rito in such a perverted way.

Mikado Ryouko
Mikado is often tasked with babysitting and looking after Celine while the other members of her house are attending school, which she willingly does even when she has to talk to someone or do work at the same time. Mikado is extremely caring and motherly towards Celine, acting much like a nanny to her and letting her wander around, play, and nap in her office.

Trivia

 * The anime never adapt the Misletoe' arc and Celine is just introduced in human form without any explanation about her origins. This leaves many anime-only viewers confused.
 * In a bonus page, Hasemi Saki reveal a scrapped story where Celine to be supposed turn into a giant and destroy part of Sainan Town but the story looked out of place with the mood of the manga.
 * She and Mikan are customers at the Stray Cat in the manga series Mayoi Neko Overrun! in Chapter 1.
 * Celine appears to be very similar, in both appeance and traits, to Alas Ramus of Hataraku Maou-sama. Both of them have plant-like origins, their basic traits are that of a toddler, and both see the main male character as a father.