Mariko is the captain of the cheerleading team. When her school played against the Furinkan High School girls volleyball team, Mariko and her cheerleading companions helped their team to win by discretely using their cheerleading batons to knock out all of the Furinkan Team, with the exception of Akane, who is saved by Ranma, who happened to be passing by.
Akane is upset about losing the game because of Mariko's interference, and Ranma tries to comfort her without much success. Upperclassman Tatewaki Kuno tries to do the same, only to be hit away and into the air by an angry Akane, who had been hugged by Kuno from behind.
Mariko and her fellow cheerleaders are walking home when the flying Kuno just happens to land right on top of her. Kuno puts a band-aid on the bump, apologizes, and leaves. Mariko, however, after seeing Kuno immediately falls in love with him. Later on when Kuno is chasing female Ranma/"the pigtailed girl" as usual, Mariko notices this and immediately challenges "Kuno's girlfriend" to a martial arts cheerleading contest, which Ranma gladly accepts in order to get even for humiliating Akane.
However, as it turns out, Martial Arts Cheerleading doesn't only involve interfering to help your team win, but also involves encouraging your team up to the point where they feel invincible, thus whoever Kuno feels loves him more would win the match. Mariko is quite good at this, but Ranma has trouble confessing "her" "love" for Kuno.
Various tactics were used by both participants, including love letters and pictures thrown by both Mariko and Ranma-chan, as well as declarations of undying love on both sides. Eventually during the match, the outcome of the Mariko/Ranma matchup turns into something which depends on a fight between Kuno and a masked kendoist who turns out to be Akane. The match ends in a draw with both Kuno and Akane knocked out.
To be added
Mariko has a comical trends- and romanticism-obsessed, extremely "feminine" "valley girl" personality and speech patterns.
She often habitually speaks in rhymes, or spells words out in Romaji characters such as M-A-R-I-K-O, much like your average cheerleader would do in a cheer. Mariko also gives her special techniques overly stylish love-related names like: "Love Confession Pom-Pom Fireworks", "Love Boomerang" or "Innocent Girl Love Letter Blast".
She was briefly in love with Kuno, due to an overly idealized personal image of him as a perfect man for her, and went to extremes in order to get him.
Her blind affection for Kuno was similar to his own for "the pigtailed girl" and Akane, going by the massive photographs of him that she plastered over her bedroom (possibly obtained from Nabiki), and that she even gladly accepted his silly mistreatment as affection (doodling on ther face and mostly ignoring her efforts). However, being a trendy social girl with limited attention-span, she very quickly "got over" and forgot about him as he was "like, so two days ago", whereas Tatewaki appears highly conservative.
Although Mariko is a legitimately vain, goofy, and in some ways superficial girl, she is actually quite cunning, capable of subterfuge or planning strategies to achieve her goals, and is rather observant about personal relationships.
A very versatile fighter with her cheerleading tools, she is willing to work hard to achieve her goals and will go quite far to succeed in them, but she seems content to manhandle rivals, not actually assassinate them.
Mariko's fighting style is based on using specialised cheerleading tools (reminiscent of how Kodachi uses gymnastic tools), for example by using batons as bludgeons, or throwing them with great stealth and accuracy, to knock out an opposing team without notice.
As it turns out, Martial Arts Cheerleading doesn't only involve interfering to help your team win, but also involves building your team up to the point where they feel invincible. Mariko is quite good at this, whereas Ranma had comparative troubles, as she/he feels very unnatural in the position.
Contradictory to Mariko's silly fluffy style, personality, and mannerisms, she easily appears to be one of the strongest young female fighters in the series, and gave female Ranma a much harder challenge than Ukyo or Shampoo were ever able to, even twice managing to knock out her opponent through some element of surprise. Then again Kodachi also did quite well when Ranma was similarly restricted to restrained, unfamiliar battle-rules, but that was much earlier in the series, before Ranma's power-up at Cologne's hands.
- Nyoibo Baton Crash: Mariko extends her baton to attack. Nyoibo is the name of Goku (from Dragon Ball Z)'s extending stick. In the manga, the spectators even make a comment about it being an obvious Dragonball reference and ask if they are in the right manga. She almost instantly beat Ranma-chan through using this move.
- Black Widow Ensnaring of the Lover Ribbons: Mariko uses spider-wed ribbons to disarm her opponent.
- Flying Sea Urchin Pom-Pom Love Bomb: Mariko's pom-poms turn into balls of spikes, which she hurls as revolving shredders towards an opponent.
- Love's Deepest Cut: Mariko throws a swarm of razor-sharp cheerleading batons.
- Cupid's Arrow Straight Down: Mariko jumps high into the air and descends, striking an opponent's head with her club. This attack was powerful enough to knock out female Ranma when the latter was distracted.
- Love Bursting Out All Over: This technique involves Mariko's team throwing her into the air while she hides behind her pom-poms. It is followed by the "Love Rival Elimination Kick."
Less useful moves:
- Quicksand of Love: Mariko is supported by her team-mates’ pom-poms, while her opponent is held in place.
- Zombie of Love: Mariko uses Kuno to attack Akane through using the following two methods:
- Mid-air Clash of Hearts: Mariko moves Kuno into the air and makes him use his blade as a shield.
- Puppet of Love Baton Storm: Mariko flings numerous batons from behind Kuno.
Completely useless moves:
- The Shower of Confidence: Mariko showers Kuno with love letters, giving him the confidence he needs in order to win.
- The Fireworks of Love: Mariko's pom-poms explode and spell out "Kuno" and "Love".
To be added
Mariko appears in the video game Ranma ½: Chougi Rambuhen. In her story, she wants to find the Maneki Neko to wish for the perfect boyfriend. When she makes the wish the Maneki Neko presents himself in a tuxedo as the perfect boyfriend.
To be added
- Mariko has many similarities with Kodachi Kuno. In the Japanese version she even has a similar laugh.
- A manga illustration showed her hair as blonde but she is a brunette in the anime. Chougi Rambuhen portrays her with blonde hair in-game, but brown hair on the manual and cover art.
- Mariko is a common Japanese name meaning "child of true benefit." This could be a reference that she benefits the teams she cheers for and ensures that they do not lose. Konjo is broken down into "today's law", which could also be an ironic reference to the fact that she helps her teams break the rules.
- Her seiyū, Yuko Kobayash also voices Atsuko, Anna and Ling-Ling.
- Her English voice actress, Jocelyn Loewen also voices Satsuki Miyakoji and Panda Doodle.