Screenshots
Hollow Heart
Phantom Doll Lab · Published by Phantom Doll Lab
Content notice: This work includes depictions of sacrifices and mutilation of the human body.
Last updated 5 Sept 2026
Hollow Heart is a growth‑simulation game about forbidden human transmutation and twisted sisterly devotion. As the elder sister, you gather materials, rebuild your little sister’s soul and body, and attempt to revive her in a more “perfect” form.
Adventure, Indie, RPG, Simulation · 2027 · More free games
About this game
Blasphemous Sister‑Obsessed Human Transmutation
Hollow Heart is a growth‑simulation game built on the theme of blasphemous, sister‑obsessed human transmutation. As the elder sister, you will do whatever you can to resurrect your beloved little sister who has died. Gather materials, strengthen her soul and body, and bring forth a sister who is ever more “perfect” and “complete.” At the end of this profane path, will you truly be able to reclaim the sister you once knew?
Human Transmutation
Your sister can be revived by offering a body and a sacrifice. To erase the sacrifice’s personality and anchor your sister’s soul, you must fuse different bodies together. Prepare stronger vessels and superior sacrifices to resurrect the ideal little sister.
Raising / Growth
After transmutation, your sister’s soul and body are fragile and short‑lived. Educate her, train her, and build a bond of trust as you face hardships together. If she reaches the end of her lifespan, use her remaining body as the foundation for the next transmutation.
Exploration / Combat
Venture out to gather the materials needed for transmutation and growth. Along the way, primitive creatures and humans bound by trivial notions of morality will stand in your path. Work together with your sister to overcome them and carve your way forward.
System Requirements
Will my PC run this? →Minimum
- OS: Windows 10
Supported Languages
Latest news
AnnouncementsOfficial
August Development Report
Hi, I'm Samezaki, in charge of graphics for Hollow Heart.This month's post is some behind-the-scenes talk about the charactersThe little sisters in the game are color-coded by attribute.Fire is red, water is blue, wind is green... following the attribute-color conventions that so many games have ingrained in us.Since there end up being a lot of little sisters, sorting them by color makes them easy to remember.It also makes their roles easy to picture at a glance.And then there's the hair — my personal obsession! The so-called "air intake" hair part*.I'm haunted by the Heisei era**, so I just can't leave it out.That's right, Hollow Heart is an air-intake-little-sister-proliferation game. ...Maybe not.The little sisters are slowly multiplying, too.Separately from the little sisters, we're also working on characters who'll get involved with the older sister.Just who is this guy!?Sanyonhu: "Oh no, this is one of those characters who's in for a rough time, isn't he!"Stay tuned for more progress and release news to come.....................!Samezaki------* "Air intake" hair — a nickname for the wing/vent-shaped hair tufts common in 2000s–2010s anime character designs, resembling a car or jet's air intake vents.** Heisei era — Japan's imperial era from 1989 to 2019, roughly overlapping with the "golden age" of anime/otaku culture Samezaki is nostalgic for.Read full article on Community Announcements (samezaki.design)AnnouncementsOfficial
July Development Report
Thank you for reading!Today, we'd like to talk about how we keep development fun.Game development is generally known to be tough work.This is especially true for long-term projects.That's why we try to keep things enjoyable throughout the development process.We use Discord for team communication, and there, a little sister character from the game helps keep our spirits up.・She greets us every day. So cute.・She summarizes what we worked on that day and praises us for it. So cute.・She's even there to chat with us. So cute.Development is a long and challenging road, but we want to make sure we never lose our sense of fun along the way.See you again next month!sanyonhuRead full article on Community Announcements (sanyonhu)AnnouncementsOfficial
June Development Report
Thank you for taking the time to read this update. This month, I focused mainly on developing the battle system. The images shown here are all from an early prototype.Although HollowHeart is a training/raising game, I am currently working on the battle system before the training system. This is because battle is where the results of the player’s training are most clearly reflected, and having the battle system in place first makes it easier to adjust stat growth and overall balance later.The battle screen is based on a typical JRPG-style layout, but several unique mechanics have been added to increase strategic depth.Please note that these features may change as development continues.Even though battles involve strategy, HollowHeart is fundamentally a raising game.Therefore, how well you can train your character before entering battle becomes very important.Balancing the relationship between training and combat will take time, and I plan to work on it carefully moving forward.Thank you for reading to the end.I will share another development update next month.Read full article on Community Announcements (sanyonhu)AnnouncementsOfficial
Thank You for 1,000 Wishlist Adds!
Thank you so much for your interest in Hollow Heart.We’re excited to share some wonderful news today — the game has officially surpassed 1,000 wishlists on Steam! 🥳🎉Your support means a great deal to us, and the entire development team is feeling even more motivated than ever.Although the release is still a little ways off, we’ll continue to post regular development updates here on Steam.Read full article on Community Announcements (sanyonhu)AnnouncementsOfficial
Origins of Development
Hello everyone, and thank you for taking the time to read this. I’m Sanyonhu, the developer in charge of game design and programming for Hollow Heart.Today, I’d like to share a bit about how this project began and what shaped its core concept.How Hollow Heart StartedI’ve always loved monster‑raising games like Monster Rancher, and for a long time I dreamed of creating a game in that genre myself.That opportunity came last November during a game jam. Our small team—engineer, artist, and sound—built the first prototype of Hollow Heart in about five days. There wasn’t much time to refine gameplay, but the atmosphere and tone of the game were born there. The jam’s theme was “No Text”, so the prototype contained absolutely no written text.Even so, the identity of Hollow Heart began to take shape.Defining the Core ConceptWhen we decided to continue development as a full project, we spent a lot of time discussing what would make the game stand out—what would truly hook players.After many conversations, we arrived at a single, striking concept:“Blasphemous Sister‑Complex Human Transmutation.”Dark, unsettling, and strangely captivating. The moment this phrase came up, I knew: this is the direction we should take.From early idea sketches……to the current in‑game visuals……the concept has remained consistent.Our Commitment Going ForwardThis core idea will not waver. We will continue developing Hollow Heart to make it even more blasphemous, even more sister‑complex, and even more evocative of human transmutation.Thank you again for reading. We hope you’ll continue following the development of Hollow Heart.Read full article on Community Announcements (sanyonhu)
