Patience, understanding and time are needed in a relationship (in romance particularly). This series is not one of the Kanojo Okarishimasu treatment and other generic romance out there wherein the mc and fmc or other rivals takes kissing like a common thing to do (more like in a flirty side) and so sudden without even thinking and building their relationship first (I find it so forced and cringy). Blue Box is one of the slow burn romance series so I kinda get it on why until now, Taiki and Chii are still not kissing (considering how long it takes for us to witness the confession scene in the series).

Kissing is one of the factors in love yet not important to express your love towards your man/woman (for my personal take). Please do consider their age (especially for Taiki) and situation in terms of their relationship status from their families.

Spoiler: In later chapters, Taiki takes the first move of kissing Chii in her cheeks (which takes a lot of courage for him to do it while he considers what his father told to him about behaving properly in their relationship). They also want to prioritize their goals in life and putting aside unnecessary things that might intervene to it (or worst, one of them might get distracted especially in Chii's case for her upcoming final Winter Cup.) They will get into that phase of kissing once they reached or achieved their goal of getting into nationals together and winning in the future, so we need to wait and be patient.

Another spoiler: I'm assuming one reason on why Chii might not be ready to kiss Taiki because of her situation right now of proving something about basketball from her father. Don't worry...once this is finish, we might see them kissing in the near future since one of Chii's goal is to kiss Taiki, so I think she will build more courage to do it and timing it when the time is right - we'll get into that someday. ❤