Kakko Warukute Kakkoii Kimi

From Bliss: Ever since they were little, Yukihisa and Takashi have always been together. However, Takashi recently started acting strange towards Yukihisa by refusing to come near of Yukihisa, baffling him. Takashi offers no explaination for his actions, causing Yukihisa to be filled with doubts about their friendship. What can Takashi be hiding from Yukihisa that's causing him to keep 1 meter away from him?