Naomi is a typical Japanese high schooler. Tired of her parents' constant bickering and her overall dysfunctional home life, one summer she decides to run away and live in the country with her good Internet friend Keisuke Iwata. Alas, she arrives at Keisuke's house to find it's burned to the ground, though the locals are oddly unperturbed by this...
She immediately finds out why when a talking skeleton emerges from the ashes and warmly greets her! Hilarity Ensues as Naomi is torn between going back home or learning to live with her clumsy, nigh-immortal boyfriend and his gruesome gift.
Originating as a one-off story, Undying Happiness is a Slice of Life horror/comedy webcomic about Naomi and Keisuke adjusting to life together and starting a family.
- Anachronic Order: The second chapter takes place thirteen years after the first, showing Keisuke and Naomi have gotten married and had a son (with another kid on the way), and later chapters jump back and forth through time to show how Keisuke and Naomi's relationship developed.
- An Arm and a Leg: In chapter 3, Naomi ends up having to saw off Keisuke's broken arm so it can regenerate properly.
- Black Comedy: A given, since one of the main characters is a clumsy guy who can heal from all sorts of injuries, from broken fingers to stab wounds to lost limbs to being burned to nothing but a skeleton.
- Bland-Name Product: Keisuke, Naomi, and their friends visit Tokyo "Dysnie" Land in chapter 3.
- Blessed with Suck: Having grown up with almost no fear of fatal injury thanks to his powers, Keisuke tends to be reckless and accident-prone, which can cause all sorts of trouble for him and his loved ones.
- Culture Clash: Poor Yusuke learns the hard way that trick-or-treating isn't really a big thing in Japan.
- Feel No Pain: The cause of many of Keisuke's family problems. Since they don't feel pain and can recover from any injury requiring nothing but time, they tend to be rather careless.
- Fingore: At the end of the first chapter, Keisuke's grandmother reveals that dinner will have to wait until her fingertips grow back.
- Good Thing You Can Heal: A lot of the comedy comes from Keisuke getting horribly injured.
- Halloween Episode: In Chapter 4, Keisuke takes his family on a trip to America so Yusuke can experience trick-or-treating for the first time.
- He Heals Up Nicely: Keisuke in chapter 1, once he heals up completely at the festival. Naomi congratulates herself for sticking it out with him instead of bailing.
- Headbutt of Love: Keisuke gives an affectionate headbutt to his son Yusuke in chapter 2. Thanks to their healing powers and immunity to pain, they end up butting heads hard enough to draw blood, to Naomi's annoyance.
- Healing Factor: Keisuke can recover from injuries that would be fatal to an ordinary human, and doesn't appear bothered by them in the slightest.
- Iron Butt Monkey: Keisuke gets injured/killed a lot. Because of his Healing Factor, this isn't a big deal for him.
- It Runs in the Family: Keisuke's powers are hereditary; his grandmother has them, and so does his son Yusuke.
- The Klutz: Keisuke tends to be rather reckless and clumsy as a side-effect of growing up with the power to regenerate from practically any injury.
- Major Injury Underreaction: Happens a few times. Usually, any reaction Keisuke has to his injuries is worrying how inconvenient it's going to be or that he's going to scare people.
- Masquerade: A few chapters revolve around Keisuke and Naomi having to keep Keisuke's powers a secret from those not in the know.
- Oh, No... Not Again!: In the first chapter, Keisuke is burned to a skeleton because he left the gas stove on. Again.
- The Pollyanna: Keisuke always tries to maintain a cheerful and optimistic spirit, despite all the troubles his powers can cause.Keisuke: Isn't it better to focus on the things that make you happy, rather than feeling down?
- Resurrective Immortality: Keisuke and his family members have this.
- Relax-o-Vision: Particularly gruesome injuries are depicted in this manner.
- Staring Kid: Keisuke runs into one of these in Chapter 3, after he's lost a forearm and clumsily tried to hide it in a shopping bag. He freaks the poor kid out even further after saving him from being run over by a train and inadvertently showing off his stubby, still-regrowing arm.
- Stripped to the Bone: In the first chapter, Naomi discovers the extend of Keisuke's powers when he regenerates from nothing but a skeleton after his house burns down.
- Unusually Uninteresting Sight: When Naomi first met Keisuke, she discovers that his neighbors already know about his power, so they don't really respond with anything besides mild annoyance even as he's wandering around as a living corpse.