Show me where in the bible it says: "two natures in one person."
We know he was truly human, so I won't make any arguments for that. As to his being also true deity:
Mat 1:18 Now the birth of Jesus Christ took place in this way. When his mother Mary had been betrothed to Joseph, before they came together
she was found to be with child from the Holy Spirit.
...
Mat 1:23 “Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel” (which means,
God with us).
Mary conceived without sexual relations; it was a creative act of God that conceived Jesus. He was to be known also as Immanuel, "God with us."
Joh 1:1 In the beginning was the Word, and the Word was with God, and the Word was God.
...
Joh 1:14 And
the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth.
Self-evident.
Php 2:5 Have this mind among yourselves, which is yours in Christ Jesus,
Php 2:6 who,
though he was in the form of God, did not count equality with God a thing to be grasped,
Php 2:7 but
emptied himself, by taking the form of a servant, being born in the likeness of men.
Php 2:8 And
being found in human form, he humbled himself by becoming obedient to the point of death, even death on a cross.
Also self-evident.
We also have Jesus's claims about himself:
Joh 3:13 No one has ascended into heaven except
he who descended from heaven, the Son of Man.
Joh 6:38 For
I have come down from heaven, not to do my own will but
the will of him who sent me.
…
Joh 6:62 Then what if you were to see the Son of Man
ascending to where he was before?
Joh 16:27 for
the Father himself loves you, because you have loved me and have believed
that I came from God.
Joh 16:28
I came from the Father and have come into the world, and now I am leaving the world and going to the Father.”
Joh 17:5 And now,
Father, glorify me in your own presence with the glory that I had with you before the world existed.
…
Joh 17:8 For I have given them the words that you gave me, and they have received them and have come to know in truth that
I came from you; and they have believed
that you sent me.
And this:
Gal 4:4 But when the fullness of time had come,
God sent forth his Son, born of woman, born under the law,
It's worth noting that this is exactly what Matt. 1:18 is talking about.
(All ESV.)
Everything about Jesus in the NT points to him being both truly God and truly man.