What is the plot?

Keita and Makoto notice Ouran acting strangely and decide to follow her one night.

Keita reveals to Makoto that Ouran is actually from an alternate timeline.

In this revelation, Keita explains that in the original timeline, Kadode and Ouran stumbled upon the alien scout Isobeyan, where Kadode used his futuristic tech in a horrifying way, convincing the alien that humanity was arrogant and violent and not capable of coexistence, leading him to relay that message back to his homeworld.

The mecha mandarin grants Makoto a look into Ooba's brain, providing a recap of the original timeline and new information about the differences between the two timelines.

In the original timeline, Kadode takes it upon herself to use the invader's tools to assist those in need, and on a sweltering summer day, she attempts to help a pregnant woman stranded at a closed railway crossing but inadvertently causes a train derailment.

Horrified by the unintended consequences, Kadode becomes devastated that her efforts to do good resulted in harm and vows never to fail again.

Ouran witnesses her Kadode kill herself in the original timeline and is given the chance by the invader Isobeyan to go to a different universe or back in time to change the pathway of events.

Ouran chooses to slide into this new world, knowing the best way to save Kadode was to make sure they never met the alien in the first place.

In this current timeline, instead of Kadode being the weird and alienated one, Ouran decides to make herself into the weird one to force Kadode to act more normal, which throws off their running into Isobeyan and avoids Kadode dealing with his devices that led to her vigilante justice and death.

Ouran proclaims herself the true villain to the class, awkwardly calling out both sets of bullies to draw their ire away from Kadode and because she is the true villain of her world, having the opportunity to stop the aliens but choosing not to for Kadode's sake.

As Ouran makes this proclamation, her leaky eyes and drooling mouth appear for the first time, a face she makes when embarrassed beyond belief but determined to power through for Kadode's sake.

Kadode's core memory of Ouran is this scene where the girl she hardly knew stood up to the bullies in class and saved her from a life of loneliness, now reinterpreted with the new information.

Oba comes across an invader being attacked by Kohiruimaki and the Youth United Front.

Oba saves the invader at the cost of Kohiruimaki stealing his invisibility cloak.

The invader reveals to Oba that a faction of invaders who hated humanity planned on letting the mothership crash and pollute the world with F-energy.

The invader, as he lies dying after the attack, speculates that their leadership had sold them a false promise of easily retaking their ancestral lands but used them as the first wave of bodies in a deliberately engineered conflict with humanity.

The invader dies after relaying this information, leaving Oba wondering what he could do to help.

Oba learns that Isobeyan was an investigator sent to Earth to confirm that humanity could be used for slave labor.

Later, Oran and Oba discover an abandoned spacecraft on the shore.

Oba voices his conflicting loyalties to Oran.

Oran kisses Oba.

Knowing that the world is about to end, Kadode arranges to meet with others.

The mothership hovering over Tokyo emits white smoke, signaling the imminent explosion of its internal reactor, which will blanket the earth with an endless rain of contaminants.

A resistance group aimed at stopping violence distributes plastic guns to its members, promising human-on-human conflict.

Ikeda, the JSDF officer involved in anti-invader operations, takes leave to visit his family.

The screen displays the message "5 DAYS UNTIL THE END OF HUMANITY."

What is the ending?

In the ending of episode 13, Kadode and Ontan (Ouran/Orin) are crushed to death by falling UFO debris, their story climaxes with Ontan's timeline shift revealed as the cause of the invasion to save Kadode, while the mothership looms toward global catastrophe in five days, and Ooba shares a kiss with Ontan amid fears of abandonment.

The episode opens with Keita Ooba and Makoto noticing Ouran (Ontan) acting strangely one night; they follow her through the shadowed streets of Tokyo under the ever-present mothership, its silhouette blotting the sky. Keita pulls Makoto aside in a dimly lit alley, his face tense with worry, and reveals to her that Ouran is not fully human--she carries memories from another timeline, a secret he's pieced together from fragmented visions and her odd behaviors, his voice low and urgent as rain patters on nearby rooftops.

Cut to Kadode and Ontan preparing for a beach trip, their small apartment cluttered with sunscreen bottles, folded towels, and half-packed bags; sunlight filters through the curtains as they laugh lightly, Ontan's eyes distant yet affectionate, her fingers lingering on Kadode's arm while Kadode chatters about escaping the city's chaos, oblivious to the weight in her friend's gaze.

Suddenly, in the middle of their preparations, a massive piece of UFO debris plummets from the sky with a deafening roar, crashing directly onto both girls in a explosion of twisted metal, dust, and blood; their bodies are mangled beneath the wreckage, Kadode's arm outstretched as if reaching for Ontan, Ontan's face frozen in a final, protective expression--the scene lingers on the rubble, blood pooling amid the debris, confirming their immediate deaths as bystanders scream and sirens wail in the distance.

The narrative shifts back to the invaders' storyline; a dying invader scout lies bleeding on the ground after an attack, his alien form twitching in a pool of viscous green fluid, gasping speculations to his comrades that their leaders never intended for them to return--they were sacrificial first-wave bodies in a engineered war to reclaim ancestral lands, his eyes glazing over as life fades, body going still.

Flashbacks illuminate the "original" timeline: young Kadode, hardened into a hitman-like figure with a scarred psyche, encounters the alien scout first; she wields advanced futuristic tech in a brutal display, firing weapons that shred the scout's defenses, her face cold and ruthless, convincing the alien of humanity's arrogance and violence, dooming any chance of coexistence as he relays the message homeward before dying.

In this original timeline, Kadode later stands on a rooftop at dusk, wind whipping her hair, her expression hollow with despair; she commits suicide by jumping, her body plummeting to the pavement below in a sickening thud, ending her life amid the indifferent city lights.

The scene transitions to Ouran in her original world, a ethereal figure with fragmented memories, choosing to slide into the new timeline; she positions herself as Kadode's "absolute," standing up to classroom bullies on her first day, drawing their ire onto herself with defiant words--"I'm the real villain here"--her posture rigid, eyes fierce, redirecting hatred to shield the lonely Kadode, forging their unbreakable bond at the cost of inviting the alien invasion.

Ooba, alone in his room lit by the glow of screens showing invader memories, grapples with insecurities; sweat beads on his forehead as he watches visions of Ouran, fearing she fully remembers her original reality and might abandon this timeline--and him--for another, his hands clenched, heart pounding with dread of loss despite the evidence of her commitment.

Near the episode's close, Ooba meets Ontan again; she gives him a cheeky smile, her voice playful yet intimate--"as long as everybody's here"--before they share a deep kiss under the mothership's shadow, her lips soft against his, arms wrapping around him tightly, a moment of raw connection amid looming doom.

The mothership above Tokyo begins emitting thick white smoke, billowing ominously from its hull, signaling the imminent explosion of its internal reactor that will rain endless contaminants over Earth. On-screen text flashes boldly: "5 DAYS UNTIL THE END OF HUMANITY," the final shot freezing on this dire warning as chaos brews below.

Fates of main characters in this episode's ending: Kadode dies crushed by UFO debris alongside Ontan, her body broken in their apartment; Ontan (Ouran/Orin) dies similarly crushed, her timeline-shifting choice to save Kadode having triggered the invasion, body entwined with Kadode's in the wreckage; Ooba survives, kissing Ontan and confronting his abandonment fears, continuing into uncertainty with the countdown; the dying invader scout perishes from wounds, revealing his leaders' betrayal; Kadode's father, referenced in flashbacks, survives with a realization of his parental failures but no on-screen death.

Is there a post-credit scene?

The search results provided do not contain information about whether Episode 13 of Dead Dead Demons Dededede Destruction includes a post-credit scene or what such a scene might depict. While the search results discuss major plot points from Episode 13--including revelations about Ouran's true nature, the timeline mechanics, and the mothership's impending reactor explosion--they do not address post-credit content specifically.

To answer your question accurately, I would need access to sources that describe the complete episode structure, including any scenes that appear after the credits roll.

Is this family friendly?

No, Dead Dead Demons Dededede Destruction Season 1 Episode 13 is not family friendly, as the overall series carries a PG-13 rating suitable for teens 13 or older, with themes and content that may unsettle children or sensitive viewers.

Potentially objectionable or upsetting aspects include: - References to a character's suicide in a prior timeline, evoking heavy emotional distress. - Implications of global catastrophe and billions potentially dying, heightening apocalyptic tension. - Intense psychological strain on characters, including embarrassment, villain self-identification, and timeline-altering desperation. - Mature dramatic and sci-fi elements like alien invasions and Faustian bargains, which carry dark undertones of sacrifice and regret.