Isn't simple to describe Ichijou's feelings, because he's a character that change his role many times in the development of the series.
In a first time we know him as a very strange vampire (he isn't afraid from the light and he doesn't sleep all the day) with very strange tastes (he lives his days reading manga), that lives a very strange life (it's normally for him to do the life of the humans).
Yuki knows a gente and kind person that always tales care of her, and that is respected from all because he's Kaname's best and closest friend.
This is one of the reasons
why we can understand how special is Taku. Isn't simple be appreciated by Kaname, eheheheh....
But many times characters like him hide a dark side, and this is Ichijou's sistuation, in my personal opinion.
Because he becomes more aggressive when he's constrict to be part of a battle (he hates fight), and in that situation he uses a sword, with the one he kills Level E vampires. In these moment Ichijou doesn't smile, he's cold and resolved.
Another his peculiarity is that he doesn't seems to desire blood. We'll NEVER look at him
snaps at a girl or just a normal human, even not a vampire. He loves sweets and candies and to stay with people.
He organized a party for his birthday inviting Yuki too, because he likes her (just like a friend, damn). In that sistuation he occasionally slashed one of his fingers and Shiki
cash in on to sucks his blood, and Ichijou leave him to do it (surely he's sadistic, as he said, but SURELY, maybe he's a bit masochist LOL).
He's always quiet but this isn't a reason to think that he's a weak boy, he's her strong with heart and body, sometimes even ironic and cinic.
When he realizes that his granpa wanted to destruct the alleance between vampires and humans, Ichijou face him even risking his life. She's very proud and brave, there's not a only thing that can stop him to protect who is important for him!
I think that that situation changed Ichijou's mind a bit, because he thought to be dead but that bitch of Shirayuki Sara saved him from death (and this is the only Sara's good action in her life) and she's a pure-blooded vampire, she manipuled his mind.
Now, Ichihou reached his comrades again in a party of the Clan family, and he tries to seems the usual Takuma, but Shiki and Rima understand that he isn't the same as always. There's something in Ichijou's heart that we can't understand. Surely he doesn't love Sara (thanks to God), but he changed his mind and now he's like a slave that follow her and her desires, even
maintaining his personality and his smile.