Nura Rikuo= Mizuki Rikuo
Used to be the Sandaime of the Nura clan. He retired, and had his son take up his position as the clan head. His grand son is supposedly leading it now. He was lazily watching the time pass by when he suddenly found himself in the middle of a dark, rainy forest in the body of an infant.
He becomes the foster son of Mizuki, who fell off a small cliff in the forest. Mizuki had supposedly followed the cries of a baby and found Rikuo, but Rikuo never shed a tear that day. Then who did those cries belong to?
His foster mom closely resembles his mother, Wakana, with her bright and kind personality. Mizuki is a man of little words, but he loves deeply, and is not intimidated by many things.
Rikuo's foster dad is a descendant of the Mizuki that saved Kitaro.
Rikuo has his memories from before, but his mental age was also slightly de-aged by his young body. His yoki and powers were also weakened as his body lacks the training. He can mostly use his powers as Nura Rikuo, but they still can and need to be trained to regain his full strength.
He can't do Matoi (鬼纏) no matter how much he trusts another yokai from this new world. His existence is an irregularity, and he will never be able to truly merge with the yokai in this life.
When Rikuo was eight, his yokai blood was awakened, and he started to change into his night form at least once every day at midnight. He tried to suppress the transformation in the beginning, but he couldn't hold back his nature any longer. He started to sneak out on walks at night. For some reason, he found his Naga-dosu at his side after his abilities came back.
On the spring of his eighth year in the new world (8 years old), he found a small tunnel made from the trees in the woods behind the old shrine. Out of curiosity, he went in and found the GeGeGe forest. The forest was dense in yoki, just like the Tono village. Rikuo finds Kitaro and Medama Oyaji in the GeGeGe house, and waited until they woke up. When Kitaro woke up, he almost mistook Rikuo for an enemy, but Medama Oyaji waking up providing an opportunity for Rikuo to explain himself. From then on, he kept coming back to the forest, and made friends with almost everyone except Kitaro.
When he got into middle school, his foster parents find out he had been sneaking out at night. Once asked why, he grudgingly showed his night form. Rikuo had been planning on moving into the GeGeGe forest when he was found out, but his family accepted him as is, and gave him permission to keep going on nightly walks.
When he told his foster mom about his other yokai friends, she started making small gifts for Rikuo to bring with him. Some of what she provided were home made, and others were from a traditional confectionery store. Even Kitaro, who was still very wary and distant from Rikuo, was baited. He is also secretly looking forward to the small treats, and every time Rikuo brings something, his eyes light up and expression softens. Rikuo will never tell him about this, because he enjoys these moments.
Rikuo was able to rank up his position from knowing about each other to friends, due to the 'bait a very guarded Kitaro with food' plan. He feels accomplished about this.
While he chose the yokai world in his last life, he still traveled between both human and yokai realms. However, in the end, Rikuo stopped associating with the human world, and started living as a full blooded yokai. Although he knows he will end up making the same decision in this world, Rikuo still tries to live between both worlds in this life too. Kitaro disapproves of this way of living. He warned Rikuo that there will come a time when he is forced to choose. Kitaro secretly doesn't want Rikuo to go through the pain of being rejected (or even worse, hurt) by the human world, though he will never admit it.
While Inuyama Mana is in a different class and they didn't know each other, Rikuo helps her carry notes to the teachers' room. This causes them to be friends. Rikuo doesn't know who Mana is, but Mana knows about Rikuo as the famous 'good guy'.
Similar to his last life, Rikuo in his human form volunteers to do most jobs others hate doing, and helps others who are troubled. Although he is known throughout the school as a 'good guy', he definitely doesn't do others' dirty works. Rikuo thoroughly corrects those who try to push their tasks onto him. He is a 'good guy', but is scary when he is angry.
Rikuo and Kitaro have not met in the human world yet, so Kitaro doesn't know what Rikuo's human form looks like. Similarly, Mana doesn't know his night form.
A/N: This is all that she has written. If she adds anything else, I will translate that too. If you want to continue the series using this premise, please do so, but leave a link so that I can both see it, and show it to the original Japanese author of this work.