Another temple nestled deep in the mountains (of Nagaoka City), Yōkoku-ji is hard to reach but rewarding to go to, in particular during rainy (June) and maple foliage (November) seasons. A temple historically visited to pray for eye-related illnesses, the grounds are surprisingly vast.
Yōkoku-ji is an example of how social media has been actively used by religious entities to popularize a previously remote location. Since around 2018–19, the hand-washing basin at the entrance and the stone wells within the temple have been transformed into seasonal flower basins. Limited stamps are sold to visitors. As a result, the temple got so popular it started to charge visitors with an entrance fee.
Unfortunately, I have not been to Yōkoku-ji any other time than during a (still comparably quiet) autumn season in 2018. My personal highlight is the second-floor garden viewing room (open during high seasons and every 17th of the month).

Admission: temple open year-round; special area every 17th or during April/June/November season.