Sekai Saionji/endings

Sekai's fate drastically differs on each ending and medium of the series. According to the, Makoto has children with Sekai and Setsuna but the official continuity is still unknown, see this.

The Good Endings
Sekai has five good endings, all of which end with her and Makoto overcoming all obstacles to be together.

The Bad Endings

 * In Bloody End, Sekai gets her jugular sliced by Kotonoha.
 * In To My Child, Sekai disappears for six months before returning to kill Makoto. In the LxH extension "End of the Folly", Sekai has given birth to a son fathered by Taisuke and left him in the care of her mother, Youko.
 * In Pushed Too Far, Sekai pushes Kotonoha into the path of an oncoming train.
 * In Forever, Sekai and Makoto witness Kotonoha's suicide and break up shortly after, haunted by the event. In the LxH extension "Blue Smile", she reunites with Makoto, informing him that she's soon to be divorced.

Kotonoha's Endings
In all seven of Kotonoha's endings, Sekai ends up alone without any malicious intent, always breaking up with Taisuke.

Sub-Heroine Endings

 * In Otome's ending, Sekai ends up alone, as with the Kotonoha endings.


 * In Hikari's two endings, Sekai is still in a relationship with Makoto while he cheats on her with Hikari and a multitude of girls, or he's in a secret relationship with Hikari and is later seen crying comically after Hikari's given birth to their baby, presumably sad rather than having any malicious intent.

Harem Endings

 * In Two Lovers, Sekai ends up in a polyamorous relationship with Kotonoha and Makoto. Along with Kotonoha, she becomes pregnant and the two plan to announce their pregnancies to Makoto for Christmas.
 * In Goodbye Sekai, she moves to Paris and has a failing long-distance relationship with Makoto.

Note that the Japanese Wikipedia classifies Setsuna's Feelings to be a Setsuna ending, even though Makoto ends up with Sekai.

Anime
Towards the end of the series, Sekai discovers that Makoto is sleeping around with other girls and, still reeling from Setsuna's sudden transfer to Paris, does nothing about it until she discovers that she could be pregnant. However, Makoto refuses to take responsibility, and the other girls stop taking an interest in him, causing their relationship to worsen. As she's making dinner for them at his apartment, he secretly reconciles with Kotonoha and tells Sekai off when she calls him during his date with the former. When Sekai confronts the two at his apartment, she has a breakdown after watching Makoto and Kotonoha make out.

The next day, she and Makoto get together for a chat, him having tried to convince her to get an abortion the night before. When Sekai goes to the kitchen to make tea, she sees her dinner from the night before having been thrown away. This becomes the final straw, and she stabs Makoto to death after distracting him with a text. She is later confronted on the school rooftop by Kotonoha, who in turn kills her by slicing her neck and cutting open her stomach, after which she concludes that Sekai's pregnancy was a lie to get Makoto's attention.

Manga
Makoto cheats on Kotonoha with Sekai, but decides to break up with her and start over with Kotonoha. Sekai amicably accepts and makes Makoto promise to treat Kotonoha right. After Makoto apologizes to Kotonoha, Kotonoha reveals she isn't angry at him but rather, at Sekai and tries to kill her, only for Makoto to shield Sekai. A week later, Sekai visits a hospitalized Makoto and after the latter receives a panicked phone call from Kotonoha's sister Kokoro, gloats to him about having killed Kotonoha. She then embraces him, telling him that they can now start over.

Summer Days/Shiny Days
In ending Paris for Four, Setsuna, Sekai, and their mothers——Youko and Mai, all end up in a harem relationship with Makoto and get pregnant. In ending Like Mother, Like Daughter, Sekai and Youko end up in a harem relationship with Makoto.

Visual Novel
Depending on which route you take, Yuuki will try to end the affair between Sekai and Makoto, but cannot convince either of them. In certain routes, Yuuki might not only attempt to kill Sekai to stop the affair, but he also attempts to molest her, only for Setsuna to intervene. Save for the endings Sacrifice and Fulfillment and Secret Fall, Makoto breaks up with her.

Manga
She and Kotonoha are revealed to be in a threesome with Makoto.