In chapter 603 while Obito is recovering we can clearly see that he is developing his wood style.
As Obito got stronger not only his sharingan grew but his ability to use wood style grew as well. Obito wasn't that old when Hashirama's cells were implanted in him meaning Obito was still in the process of unlocking his full power, that's why you could very much say that his wood style can be considered his natural ability along with his sharingan. This could change our whole view on Obito and he can be more powerful than we think. If Obito decides to go against Madara, him and Kakashi together with their sharingan can play a big roll for stopping Madara
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As Obito got stronger not only his sharingan grew but his ability to use wood style grew as well. Obito wasn't that old when Hashirama's cells were implanted in him meaning Obito was still in the process of unlocking his full power, that's why you could very much say that his wood style can be considered his natural ability along with his sharingan. This could change our whole view on Obito and he can be more powerful than we think. If Obito decides to go against Madara, him and Kakashi together with their sharingan can play a big roll for stopping Madara