In both manga, a boy falls in love with a girl who isn't really a girl at all, but is actually a femmine, cross-dressing boy. Steam Trap is a short, cute (but ultimately pointless) one-shot, while Sazanami Cherry is a little longer and has more of a story to it. Still, if you like cute manga about guys falling for 'traps', you may want to check out both.
Both are one-shots about a boy who falls in love with a 'trap' (femimine boy who crossdresses/looks like a girl). Also, both manga take place in a hot spring. If you like one, you might like the other.