Adachi Asumu, unsure of what he wants to do with his life and unconfident about taking an entrance test to a well known band school goes on a trip with his mother one day. They travel to an island by boat and suddenly a young girl falls over the side of the boat. A man races to her rescue, jumping overboard himself, just in time to grab the girl. Asumu takes notices and thinks the man who saved the girl, Hibiki, is a bit odd. The two part ways as Asumu and his mother get to an island. There Asumu encounters a Makamou and witnesses Hibiki become an Oni.
Asumu and Hibiki meet up many more times at a sweets shop that the Takeshi organization owns and operates from. It is the meeting ground for many different Oni around Japan. Asumu ends up meeting the trumpet wielding Oni, Ibuki and Ibuki's supporter. Supporters are exactly what they sound like, people who support the Oni on their missions, and in many cases are training to be Oni themselves. Ibuki's supporter doesn't feel Asumu should be around Hibiki as he only drags Hibiki down. Eventually he ends up winning her trust and respect.
Later on the third and fourth series riders appear. Todoroki and his master Zanki, Zanki is an aging Oni who can't fight as well as he used to. Todoroki steps up to take his place as he becomes an Oni with the "ki" suffix, signifying that he is no longer the student. Todoroki is a rookie and still has much to learn and treats Ibuki and Hibiki as his superiors as they have more experience, even though Ibuki is younger than Todoroki himself.
Hibiki, Ibuki, Todoroki and Zanki make up the main Oni cast of the series. Many other Oni appear in the series, but they're in the series for an episode or two at the most. Over the course of the show other characters join the main cast, even a young boy who tries to get Hibiki to make him his apprentice.
Download01 - The Echo of bugger
02 - The Giant Spider
03 - The Voice decadent
04 - The Race enlightening
05 - Melting Sea
06 - Beat of Soul
07 - The blast Oni
08 - Wind cut
09 - The Evil contort
10 - Oni Waiting In Line
11 - Swallowed By the wall
12 - Secrets disclosed
13 - Angry Destination
14 - Douji Devorador
15 - Thunder weakened
16 - Torodoku Oni
17 - City in Mira
18 - Hurricane Impervious
19 - The Torn of the Warrior
20 - The sound that purifies
21 - Demons Gathered
22 - Turning a Cocoon
23 - Training of summer
24 - Burning Red
25 - Competition Blue
26 - Notched the Days
27 - Turning the Loop
28 - Eternal Evil
29 - Brilliant Boy
30 - Premonition of Education
31 - Overcoming the Father
32 - Drop the Voice
33 - Armed Saber
34 - Amado Bonito
35 - Lost Angel
36 - Shuki Faminta
37 - Lightning relived
38 - Broken OnGenki
39 - Your Home
40 - Orochi is approaching
41 - Raising the Student and Teacher
42 - Demons fierce
43 - Body Which Can not Change
44 - Secret Forbidden
45 - Dying from a Glorious Death, Zanker
46 - The Way Home of Oni
47 - Speaking to the Past
48 - The Dream of Tomorrow (Final)