  We calculate boundary states for general string fields in the KBc subalgebra
under some regularity conditions based on the construction by Kiermaier, Okawa,
and Zwiebach. The resulting boundary states are always proportional to that for
the perturbative vacuum |B>. In this framework, the equation of motion implies
that boundary states are independent of the auxiliary parameter s associated
with the length of the boundary. By requiring the s-independence, we show that
the boundary states for classical solutions in our class are restricted to
\pm|B> and 0. In particular, there exist no string fields which reproduce
boundary states for multiple D-brane backgrounds. While we know that the
boundary states |B> and 0 are reproduced by solutions for the perturbative
vacuum and the tachyon vacuum, respectively, no solutions reproducing -|B> have
been constructed. In this paper we also propose a candidate for such a
solution, which may describe the ghost D-brane.
