Dragon Baby (Legendary) !

After Kaguya ate the divine fruit , just like in Canon , she beat the pursuers and manipulated the divine tree to wrap up most humans nearby , transforming them into white zetsu to protect the planet from her kin , who she knew for sure would be coming ...

As for the strangeness of the chakra fruit , since she didn't notice anything wrong with the power it gave , she ignored it directly ...

((( this should also be because of the divine tree madness affecting her wisdom )))

and as she was pregnant , she just fortified the place around the divine tree , and waited until birth ...

Tenma , just watched everything quietly from inside her ...

That's right , the strange blood in the chakra fruit was actually him !

he took the opportunity to escape the divine tree , especially after he completely absorbed its DNA and enhanced his own bloodline ...

as for why kaguya didn't notice his existence , maybe because she considered him as part of the chakra fruit and didn't observe further...

(((( a clearer explanation in an example :

like how after Venom fused with Peter Parker, Peter parker's spider-sense didn't notice the danger from Venom anymore , and didn't work on Venom ...

that is because after Venom fused with him , his spider-sense considered Venom as just a part of his body ))))

And all this was according to his Plan !

a plan , to also cheaply get a copy of the pure otsutsuki bloodline of Kaguya !

what he is currently doing , is seeping part of her blood , to assimilate the otsutsuki valuable DNA ...

and he will take the opportunity to escape kaguya's body , when she gives birth to the twins , hagoromo & homura !

___________

Kaguya was heavily breathing , and she held her pain while she gave birth to the sons she sired from a mortal human of this world ...

sons she didn't know would turn against her later ...

(((( honestly though , what ingratitude & unfilial actions ...

even though she transformed some people into white zetsu , she was still their mother after all !

they didn't need to be so cruel as to seal her in isolation for a thousand years , right ??? ))))

Tenma , took the opportunity after kaguya was tired when she gave birth to the twins , and gathered his own blood , and some of kaguya's , and created a baby's body for himself ...

then , he quickly rushed out of kaguya's womb !!

Initially , he didn't plan for such a thing , but after he was greatly weakened , even if he could still freely come out of kaguya's body , he would be noticed by kaguya's eyes right away ...

so , he decided it would be safer if he posed as one of her babies !!

so , Tenma , The Dragon , was truly and literally rebirth at this moment !

As son to the Rabbit Goddess Otsutsuki Kaguya !

As brother to the Legendary sage of six-paths Otsutsuki Hagoromo !

And as brother to the progenitor of Hyuuga clan and branch Otsutsuki family on the moon , Otsutsuki Homura !

Otsutsuki Heiryu !