You coughed up blood, cried blood until your blood almost filled all your clothes..

Your actions of trying so hard to protect him made Obito realize that he shouldn't continue to love Rin, who died long ago in the Third Shinobi World War. Plus, Naruto's words also succeeded in piercing and making Obito realize that he was needed. After the Fourth Ninja World War ended, Obito began to focus on things that could calm him down.for a while Kakashi chose you as someone who cared for and accompanied Obito and that's when...day by day, month by month his feelings began to grow for you.

Obito knows very well that he and you are quite far apart in age, but this feeling just grows and is difficult to get rid of.