~上に
On top of that, another related fact is true
You’ll be able to strengthen a description by adding another fact pointing in the same positive or negative direction.

この道の駅は料理が美味しい上に、景色も素晴らしい。
kono michi no eki wa ryouri ga oishii ue ni, keshiki mo subarashii.
What do you think this sentence means?
On top of having delicious food, this roadside station's view is also wonderful.
Add another fact in the same direction
~上に means "on top of that" or "not only... but also...". It reinforces a description by piling on an additional fact that shares the same positive or negative quality.
田中さんは優しい上に、話も面白い。
tanaka san wa yasashii ue ni, hanashi mo omoshiroi.
Tanaka-san is kind, and on top of that, fun to talk to.
今日は疲れた上に、お腹も空いた。
kyou wa tsukareta ue ni, onaka mo suita.
Today I am tired, and on top of that I am hungry.
Attach 上に to plain forms
Attach 上に to plain forms of verbs, い-adjectives, な-adjectives (using な or である), or nouns (using の or である). Both facts must be in the same direction (both good or both bad).
昨日は雨が降った上に、風も強くて大変だった。
kinou wa ame ga futta ue ni, kaze mo tsuyokute taihen datta.
On top of the rain yesterday, the wind was also strong and it was miserable.
~上に vs ~反面
~上に adds a second fact in the same direction: good and good, or bad and bad. ~反面 turns to the other side: good but bad, or bad but good.
~上に, on top of that
この部屋は広い上に、明るい。
kono heya wa hiroi ue ni, akarui.
This room is spacious, and bright on top of that.
Both facts are good.
~反面, but on the other side
この部屋は広い反面、暗い。
kono heya wa hiroi hanmen, kurai.
This room is spacious, but on the other hand it is dark.
One good fact, one bad fact.
このアパートは古い上に、冬は部屋の中もとても寒い。
kono apaato wa furui ue ni, fuyu wa heya no naka mo totemo samui.
This apartment is old, and on top of that, it’s very cold even inside in winter.
新しい先生は教え方が上手な上に、質問にも丁寧に答えてくれる。
atarashii sensei wa oshiekata ga jouzu na ue ni, shitsumon ni mo teinei ni kotaete kureru.
The new teacher explains things well, and on top of that, they answer questions carefully.
今日は財布を忘れた上に、スマホも家に置いてきてしまった。
kyou wa saifu o wasureta ue ni, sumaho mo ie ni oite kite shimatta.
Today I forgot my wallet, and on top of that, I left my phone at home too.
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