I was exactly this type of best friend for one girl for the longest time, until she figured it out. decisive friendship-ender right there.
Seriously, ouch! Even if your friendship doesn't immediately implode it is sadly quite common for all that tension and unanswered emotional baggage to pile up and for your bond to eventually buckle under the weight no matter how desperately you labor to keep it all from happening.
This story really captured a very realistic glimpse of how bittersweet unrequited love can be.