Yes, you should stay in Koukaki and in Nikos’ appartment! We had the best time. The location was great, the neighborhood is very relaxed, so many things to do and see nearby and great restaurants/cafes options (which are not yet touristy). Nikos was a welcoming host and very quick in his communication. The appartment had everything we needed for our 4-week stay and the balcony was also very nice to have! We have definitely fallen in love with Athens :)