>>279714195Debatable; the reason that is given within the series is that Kaworu pretended to act that way to get close to Shinji and let his guard down so he could infiltrate NERV and get into Central Dogma as part of his role as an Angel, which is why Shinji has such a meltdown about how Kaworu 'betrayed' him.
However, there's also some stuff around the fact that since Kaworu is basically completely devoid of any concept of how humans and social behaviour works, he feels that way about everyone. However, because Shinji is the only one who basically needs complete validation from somebody, he's the only one who responds like that (as opposed to how Asuka, Misato, Akagi, etc all act)