Demon Dog of the Sea

, also known as Killer Swimwear, is the 285th chapter of the manga and the first chapter of the Demon Dog Swimsuit Arc.

The Tendos and Saotomes all go to the beach for a day of relaxation, but are surprised to find it is deserted. In the ocean they see signs warning of a dangerous dog, which seems like an odd place for such words of caution. After talking with some of the townspeople they discover that a demon dog lives in the sea and drags young girls to their deaths each summer. Ranma is sent to investigate and as he swims out to sea, where the demon crosses his path.

To the Beach
The Tendos and Saotomes arrive at the beach ready for a day of relaxation. Oddly though there seems to be nobody else anywhere near the beach. After noticing that all the local stores are still open, the group notice some signs in the ocean warning against swimming in the Ocean due to a dog, leaving the group in great confusion. Meanwhile, Soun and Genma learn from the local store owners that for several years now that every Summer the dog appears and begins dragging women to the bottom of the Ocean with it. Some of the store owners then begin to sob at the thought of going out of business due to this Dog, causing Soun and Genma to agree to help them out.

Back on the beach, Soun explains about the situation and tells Ranma (who's in his female form) to go deal with the Dog as it will only go after young women. Ranma descends towards the Ocean floor, where after seeing a bright light emanate is attacked by the Demon Dog. The Demon immediately swipes at Ranma, but she avoids it. However, when Ranma goes in to attack the Demon herself, she passes right through it. Ranma soon deduces that the Demon must be an illusion and then notices a small shrine on the Sea Bed. Without a second moment's thought, Ranma swims down to the shrine and punches it, when a strange blast suddenly engulfs her...

That Evening
When Ranma comes-to, she's surrounded by the Tendos and Genma, who are all glad that Ranma's finally awoken. Ranma's thoughts quickly turn to the Demon and she asks if she was able to defeat it, to which Akane replies that she hasn't exactly defeated it and her and Nabiki point to Ranma's body. Throwing back the blanket which was over her, Ranma is shocked to find herself wearing a new, and very ugly, Swimsuit.

Ranma demands that Swimsuit be removed, but Soun and Kasumi explain that they tried to remove the Swimsuit, but unfortunately it won't budge. This prompts Ranma to try ripping the suit herself, but to no avail. Genma then brings out a pair of scissors, but the on the swimsuit quickly consumes the scissors. The swimsuit then proceeds to cry and begins revealing it's history.

The Swimsuit explains that it was being worn by it's original owner they went out on a date with Natsuhiko, where he was meant to compliment the swimsuit. Natsuhiko, however, suggested the swimsuit's owner she wear a different swimsuit and it was thrown away. The swimsuit continues by saying that it couldn't rest in peace so now waits for Natsuhiko to compliment it. When Akane questions why it's attached to Ranma, the swimsuit reveals that if Natsuhiko doesn't compliment it before the Sun sets tomorrow, it will return to the Ocean and take Ranma with it, where she'll drown.

Finding Natsuhiko
Obviously against the idea of drowning, Ranma desperately tries again to remove the swimsuit, whilst the others go on a frenzied search for Natsuhiko. There search doesn't long, however, as Natsuhiko turns out to be one of the local store owners who Soun and Genma talked to earlier. Ranma swiftly moves in to have Natsuhiko compliment the swimsuit, but Natsuhiko just suggests a different swimsuit for Ranma to try on.

After being hit by Ranma, Natsuhiko decides he'll lie and says that the swimsuit isn't that ugly, however, the swimsuit doesn't recognise Natsuhiko. Ranma tells the swimsuit it's Natsuhiko, but the swimsuit remembers Natsuhiko as a young, handsome, man not like the old man he is today. Soun soon suggests that they need to find someone who looks like Natsuhiko, but Akane reminds him that the beach is deserted and asks where they're going to find anyone. At that moment, a shadowy figure appears and declares that he's found them... As Ranma, Nabiki and Akane are surprised at the appearance of this person, the swimsuit declares that this person is Natsuhiko.

Cast in Order of Appearance

 * Akane Tendo
 * Ranma Saotome (female)
 * Nabiki Tendo
 * Kasumi Tendo
 * Genma Saotome (panda)
 * Soun Tendo
 * Natsuhiko (debut)
 * Cursed Bathing Suit (debut)
 * Cursed Bathing Suit's original owner (flashback, debut)
 * Tatewaki Kuno

Trivia

 * The strange dog creature on the Swimsuit is a "" or "Lion Dog". They are statuary guardians of who work in pairs. Komainu are like the more human-like "Myo" guardians who also work in pairs. One of the Komainu (and myo) will have an open mouth saying "Aaa" while another will have a closed mouth saying "unnn". This concept is known as ""
 * The concept of "A-un" was also used for the name of A–Un, Sesshōmaru's in InuYasha.