Sakurahime Azuma bunsho (The Cherry Blossom Princess of Edo)

At a certain point in the play, Seigen is first disfigured by poison, and then dies when Sakurahime accidentally pushes him into a grave that had a knife in it. From this point on, Seigen continuously haunts Sakurahime. His ghost chases all her customers away, and the brothel owner forces Gonsuke to take her back. Seigen, who has acquired knowledge about Gonsuke's secret wrongdoing from beyond the grave, manages to communicate to Sakurahime that in fact, Gonsuke is the enemy of her family and that she must kill him. When she finally does so, Seigen's spirit is pacified.

How does Yoshitoshi hint at Seigen's ghost?