The characters in this design are styled on Japanese Kanji characters, but are actually in English. If you look closely, you can read what this tshirt says.
In Zen Buddhism, “Kill the Buddha” refers to how one should not worship and idolise scriptures, teachers, or statues, but rather trust in one's own abilities, in one's own heart and mind. Obviously, nothing literal should be taken from this design.
By externalising spirituality, one can become caught up in acquiring knowledge and spiritual attainments, adding another retreat or technique 'notch to the belt', so to speak. Therefore, the idea behind the design is very much related to _spiritual materialism_.
The central character means ‘Buddha’ in Japanese Kanji.