Tanabata

Tanabata (七夕) is a Japanese festival derived from the Chinese festival Qi Xi (七夕), "the Night of Sevens". It was imported to Japan during the Heian period.

The festival is based on the legend of two Star-Crossed Lovers, Orihime the weaver and Hikoboshi the cowherd (Zhinü and Niulang respectively in Chinese), symbolized respectively by the stars Vega and Altair. Throughout the year they are separated by the river of the Milky Way, but for a single night each year, on the seventh day of the seventh month of the traditional lunisolar calendar, one of them is allowed to cross and they can be together. The method of crossing varies depending on the storyteller, but the most popular and romantic way is by a bridge of birds, often specifically magpies, appearing between them.

In China, Japan, and Korea (where it's called Chilseok) the festival is the traditional equivalent of Valentine's Day in the Western world. The Japanese generally celebrate this day by writing wishes on tanzaku paper, and hanging them on bamboo, sometimes with other decorations. The bamboo and decorations are often set afloat on a river or burned after the festival, around midnight or on the next day.

Examples of Tanabata include:

Anime and Manga

In Umineko no Naku Koro ni, there is a side-story called "The Witches' Tanabata", in which the audience learns about the witches' philosophies when it comes to granting Tanabata wishes.
Aoi of Ai Yori Aoshi was born on the day of Tanabata, and at one point is seen hanging tanzaku on bamboo.
Suzumiya Haruhi revolves around this trope. On July 7, on one Tanabata, Haruhi meets the mysterious John Smith, actually Kyon who went back in time, making her start to have beliefs in supernatural beings, thus driving the show - not to mention she was trying to write letters to Hikkoboshi and Orihime at the time. Three years later, she forces the SOS Brigade to write wishes and even calculates the exact amount of time it will take said wishes to reach Vega and Altair (25 and 16 years, respectively), and tells them to expect them to receive the responses to those wishes at that time. She then starts to think about the mysterious person she met those years ago, to an oblivious Kyon, who hasn't gone back in time yet. Also, in the Disappearance timeline, Kyon returns to the Tanabata of three years ago to make sure Haruhi remembers "John Smith", although this trip is mainly to meet Yuki and the older Mikuru in order to ensure his universe is restored to normal.
The anime and the manga versions of Ranma ½ have two different Filler stories based around Tanabata. In the manga, a variant of the habit of writing wishes on leaves is used as the basis for a Red String of Fate effect, with Ranma having to struggle to keep his and Akane's leaves together and avoid their leaves being tied to those of other people. The anime episode is a tale where Akane falls off of a roof and then meets Princess Orihime (referred to in the dub simply as "Princess Ori") in person, who has descended from the Milky Way to seek out Hikoboshi ("Kengyu the Cowherd" in the dub), her fiance, who has gone missing. As she explains over the course of the episode, the two of them are intended to wed and carry on the Milky Way School of Martial Arts, but she got into a fight with Hikoboshi over his lacksadasical manner and laidback attitude, so now he's come to Earth in a huff to challenge and defeat earthly dojos to prove he is a strong fighter after all... but the Princess's father will make her marry another man if he hasn't returned to the Milky Way by the end of the festival. The episode ends with Akane waking up to discover she apparently was having a dream while concussed after falling off of the roof at the episode's beginning, though there is an Or Was It a Dream? twist.
A particularly heartwarming episode of Hidamari Sketch takes place on Tanabata. Sae and Hiro have an argument and spend the day avoiding one another until Miyako and Yuno help them patch up their differences, and in the evening they decorate a bamboo together and hang wishes on it.
Karara's first appearance in the Keroro Gunsou anime included her learning about Tanabata and making a wish. This directly ties into Tamama and the others finally learning her real gender, as her wish was to become Tamama's bride.
In Chuuka Ichiban, Mao is inspired by the legend of Tanabata (the original Chinese version, of course) in making a noodle dish made of squid ink to represent the night sky and pearl dust to represent Orihime and Hikboshi, respectively.
In Lucky Star, this is the Hiiragi twins' birthday. It's also Ponytail Day because the legend says Vega had a ponytail, so they try wearing their hair in ponytails for a bit.

Tsukasa: Vega and Altair... I hope they meet this year... twinkle twinkle twinkle...

The anime version of Rurouni Kenshin had an episode where Kaoru expected Kenshin to treat her to something special for the holiday but Kenshin, who forgot about the holiday, mistook her hints for reminders of her birthday (which was months away). To make matters complicated, Kenshin found a ring inside a fish he caught and, not only forgetting about Tanabata but also not knowing about the Western tradition of engagement rings (which Kaoru and Tae were familiar with), gave her the ring... so Kaoru was now believing Kenshin proposed to her. Later on, by chance, Sanosuke meets the man who lost the ring (and is about to commit suicide because he threw the ring away in the middle of a fight with his girlfriend and fell into depression when he realized what he did) and learn about the tradition. Seeing Kenshin's face when he understood the mess he got himself into, it was hard to remember he's a feared assassin. It all ended more or less well: the ring was retrieved from Kaoru and then given back to the dude (who handed it to his girl), and Kenshin gave Kaoru a flower bouquet to make up for it. (And Tsubame and Megumi also got flowers from Yahiko and Sano).
Inoue Orihime of Bleach had a running Tanabata theme given her name. This was lampshaded a couple of times in colorspreads: One by strategically giving her a 7/7 (the seventh day of the seventh month) and another by having her alternate name translated as Vega Highwell (Vega being the star pertaining to Tanabata's Orihime).

Comic Books

The Usagi Yojimbo story "Runaways" explicitly references the myth with Usagi and the princess he had fallen for even attending the festival.

Live Action Television

Kamen Rider Den-O uses Tanabata as the running theme for Kamen Rider Zeronos; his two primary forms are called Vega and Altair, and his Imagin partner is named Deneb and is modeled on tengu (among other things). The theme of Star-Crossed Lovers also applies to Zeronos' user Yuto Sakurai and his fiance Airi Nogami, separated because Sakurai is hiding in the timestream to protect their future child, and had to erase Airi's memory to keep her safe too.

Literature

Bridge of Birds: The actions of Master Li and Number Ten Ox become interwoven with the Qi Xi story, although the heroes don't realize this when they first set out.
Nona celebrates this in the British children's book Miss Happiness and Miss Flower. Nona's actually Anglo-Indian, but became interested in Japanese culture through her Japanese dolls.
As a highly romantic story, it has been a popular topic in Chinese and Japanese poetry for centuries. They also used online college homework help.

Video Games

We Love Katamari includes a stage where players roll up all the planets and stars they've created, with the rolling up of the sun as the ultimate objective. This stage includes numerous Easter Eggs, such as the stars Vega and Altair, on which ride small human forms that shout "Hikoboshi-sama!" and "Orihime!" as you collect them.
- Beautiful Katamari on the Xbox 360 features a downloadable stage called "Lovers' Loom", where you are asked to roll up fabric and wool to make the star Vega. When completed, the King turns your Katamari into a five-pointed star with Orihime and Hikoboshi sitting on the arms.
Referenced in Persona 3: after SEES figures out how to predict when certain bosses will appear, Akihiko comments that one upcoming battle will be "a Tanabata special bout". Humorously it's the battle against the Hierophant and Lovers Arcana, which represent tradition and choice or the misuse of tradition and lack of choice, and also is the infamous Love Hotel battle.
The plotline of the story is involved intimately in the background of Mega Man Star Force 2, and the involved characters have their names maintained appropriately across localizations. Orihime is the Main Villain of the game, and in English is named Vega for the star.
Jirachi from Pokémon is a star-shaped legendary Pokémon that is supposed to wake up once every thousand years, and people upon seeing it will write wishes that Jirachi will grant onto small pieces of paper and placing them on Jirachi's head.
In Katawa Shoujo, Yamaku High School has a festival organized around Tanabata. You only get to see it in Shizune's route, though.
- Tanabata is heavily discussed in Lilly's route as Hiseo promises to take her to the festival. Appropriately, that does not happen because Lilly and Hiseo have their own Star-Crossed Lovers situation. Whether this is permanent depends on the player's actions.
While this hasn't been played into plot, yet, BlazBlue's Litchi Faye-Ling had her birthday exactly at the Tanabata day (July 7). She's also the resident Love Martyr.
In Hatoful Boyfriend, the heroine gets to see the wishes of the birds she's the closest to at Tanabata and make a wish herself to conquer the world by force, rule the world from the shadows, gain the Mad Love of a Fallen Angel, or become a famous artist.
In zOMG!, Shrine Maiden Katsumi asks you to deliver an off-season wish to a Wish Tree in Zen Gardens (she is wishing for the safety of others in the Animated attacks). The wishes in the Wish Tree turn out to be Animated themselves-- but they were created almost completely in goodwill, so they're mostly neutral/benevolent towards humans.