The story begins when high school student Kazuki Muto is killed one night saving a mysterious girl from a monster, only to wake up in his school dorm, believing it to have been a dream; however, he soon finds out that dream wasn't a dream at all when a giant serpentine monster attacks him and his sister. Tokiko Tsumura, the girl he saved, explains that the monster is a homunculus. Kazuki had been attacked and killed by it when he was rescuing her; however, she, feeling responsible for him, revived him by placing a Kakugane medallion in his chest, serving as a replacement heart.
| Title | Air Date | Duration | ||
|---|---|---|---|---|
| Season 1 | Episode 1 | A New Life | 2006-10-04 | 25 min |
| Season 1 | Episode 2 | The True Form Homunculus | 2006-10-11 | 25 min |
| Season 1 | Episode 3 | You've Become a Little Stronger | 2006-10-18 | 25 min |
| Season 1 | Episode 4 | Another New Life | 2006-10-25 | 25 min |
| Season 1 | Episode 5 | To Protect Someone | 2006-11-01 | 25 min |
| Season 1 | Episode 6 | The Butterfly of Black Death | 2006-11-08 | 25 min |
| Season 1 | Episode 7 | Whether or Not You're a Hypocrite | 2006-11-15 | 25 min |
| Season 1 | Episode 8 | A Night in the Dorm | 2006-11-22 | 25 min |
| Season 1 | Episode 9 | The Hayasaka Twins | 2006-11-29 | 25 min |
| Season 1 | Episode 10 | It Seems We're Well Matched | 2006-12-06 | 25 min |
| Season 1 | Episode 11 | 'Til Death Do Us Part | 2006-12-13 | 25 min |
| Season 1 | Episode 12 | Carnival | 2006-12-20 | 25 min |
| Season 1 | Episode 13 | Signs of Death | 2006-12-27 | 25 min |
| Season 1 | Episode 14 | Who Are You? | 2006-12-27 | 25 min |
| Season 1 | Episode 15 | An Intermediate Existence | 2007-01-10 | 25 min |
| Season 1 | Episode 16 | New Strength | 2007-01-17 | 25 min |
| Season 1 | Episode 17 | When Dawn Comes | 2007-01-24 | 25 min |
| Season 1 | Episode 18 | The Escape | 2007-01-31 | 25 min |
| Season 1 | Episode 19 | As Long As I Can Protect You | 2007-02-07 | 25 min |
| Season 1 | Episode 20 | With Strength and Spirit | 2007-02-14 | 25 min |
| Season 1 | Episode 21 | Gone Into Flame | 2007-02-21 | 25 min |
| Season 1 | Episode 22 | A Decision is Required | 2007-02-28 | 25 min |
| Season 1 | Episode 23 | Boy Meets Battle Girl | 2007-03-07 | 25 min |
| Season 1 | Episode 24 | When You Die, I'll Die with You | 2007-03-14 | 25 min |
| Season 1 | Episode 25 | No One Could Ever Take His Place | 2007-03-21 | 25 min |
| Season 1 | Episode 26 | Period | 2007-03-28 | 25 min |
| Visual Effects | Hatsue Kato | Character Designer |
| Visual Effects | Akio Takami | Character Designer |
| Visual Effects | Akio Takami | Supervising Animation Director |
| Writing | Nobuhiro Watsuki | Comic Book |
