Shin, the rocker from Episode 6, has been turned into a Madou Horror.His song was heard in Episode 10 in a music player despite his previous reluctance (and inability to perform well without a Horror's scale) to record it so he might have been forced. That or he just gained enough willpower and improved.
Hakana, Ryuga's mom, is the daughter of Kouga and Kaoru.
Yami wo Terasu Mono will be the story of......Ryuga restoring the armor of Garo to its original state, just like how in The Final Odyssey, Tiga had to regain the form he had in his series by regaining his light.
Ryuga's mother was a Makai PriestBut Ryuga doesn't know that.
Yami wo Terasu Mono is NOT a sequel, but a PREQUEL.After Taiga's death, Kouga was too young to become Garo, but a replacement had to be found in the interim. Ryuga is chosen, using a Makai process that allows someone outside the bloodline to carry Garo, but not without some unfortunate side effects like losing the shine. It's up to Ryuga to fix that shenanigan by the time Kouga is ready.
Ryuga's absent father was a Makai KnightBut like with the WMG that his mother was a Priestess, he doesn't know this. His father was likely KIA either when Ryuga was young or before he was born by a Horror, possibly even one connected to Kaneshiro. It's even possible that his father was Kouga's actual successor as GARO given all we really know about Ryuga becoming GARO is he found the sword. If his father was GARO, then when he was killed the Kaneshiro's did something to drain Garo's shine to create Madou Horror.
Takeru will replace the right hand he lost with a hook.He used to be a pirate after all.
Kaneshiro Tousei is a descendant of Rekka.In Garo: Red Requiem, his actor played Rekka's dad, and Tousei reveals that his mother came from a line of Makai Priests, and he found a whole bunch of Makai Priest gear in an attic box, and taught himself some basics. It could well be that he's descended from Rekka, whose line has since diminished, much in the same way the GARO armor is diminished.