Hinata would be overjoyed. She has loved Naruto for a long time, so his proposal would be like a dream come true for her. She might start crying tears of happiness and immediately say yes without hesitation.
Hinata might be very hurt. She's a sensitive person, so Naruto yelling at her could make her feel small and sad. She might start to doubt herself and her abilities.
One possibility is that Naruto would plan an elaborate and very public proposal. Since he is a bit of an attention - grabber, he might do it during a big festival in Konoha. He could gather all their friends and family, make a big speech about how Hinata has always been there for him, through his toughest times, and how he realizes she is the one he wants to spend his life with. Then, he would get down on one knee and present her with a ring.
Naruto would probably be extremely hurt. He has always considered Hinata a friend and perhaps more. Betrayal from her would be a huge blow to his trusting nature. He might initially be in denial, not wanting to believe that Hinata could do such a thing.
Hinata might be shocked at first. She has always adored Naruto, and this sudden act of aggression from him would leave her stunned and unable to process it immediately.
In a fanfiction, Naruto might plan a big public proposal. He could gather all their friends and family in the Hidden Leaf Village. He would make a big speech about how Hinata was the one who saw him when others didn't, and her love changed him. Then, with everyone watching, he would pop the question.
Naruto might be shocked at first. He could stand there frozen, unable to believe what he's seeing. His face would probably show a mix of confusion and hurt.
Naruto would be extremely hurt. He loves Hinata deeply and to find out she cheated with Kiba would be a huge blow to him. He might go into a state of shock and disbelief at first.
He could also become very sad and withdrawn. Naruto has always valued his relationships, and losing Hinata's love would be a huge blow to him. He might start to question himself and wonder what he did wrong.
There could be a fanfic with this title, but the use of 'lemon' makes it a bit suspect. In the world of fanfiction, there are so many different takes on Naruto and Hinata's relationship. But if it's a 'lemon' fanfic, it's likely to contain adult - themed content. So, if you're looking for proper, non - inappropriate fanfics about them, you should look for ones that are rated for general audiences.
Naruto would be over the moon. He's always been a family - oriented person deep down. He'd probably start blabbing to all his friends about how amazing Hinata is and how excited he is to be a father.