Here is the full list of all 50 Summer with Mia Season 1 achievements.
Acquired all other achievements
Chose to play without NTR when the game started
Played all the bonus scenes
Finished the main story
Finished the "farewell" scene
Finished going to a motel twice
Finished getting leverage on Emma
Finished having fun on your couch
Finished Emma's "payback"
Finished Emma getting leverage on you
Finished not getting caught by Mia
Finished visiting a special motel
Finished a perfect late night visit
Finished Mia's third show
Finished Emma's favorite pastime
Finished a successful massage
Finished getting a surprise from Mia
Finished Mia's second show
Finished getting tricked by Mia and Emma
Finished shooting your first short film
Finished a late night visit for the second time
Finished helping Mia with clothes shopping again
Finished a certain late night visit
Finished Mia's first show
Finished spying while getting distracted
Survived Mia's revenge
Successfully "killed a spider"
Finished getting Sam to help you with Mia
Finished helping Mia try on some clothes
Finished getting through the storm
Finished some much needed assistance
Finished playing truth or dare at Sam and Emma's
Finished the barbeque
Finished a quickie with Mia
Finished helping someone go to bed
Finished your first time with Mia
Used the Panic button once
Finished watching Mia change
Finished Mia's attempt to tease
Finished playing blackjack with Mia
Chose correctly when talking to Tatjana
Finished tricking Nathan to help you with Mia
Didn't miss the password for Mia's laptop
Tried the cereal last
Finished watching Mia do yoga
Finished spying on Mia in the bathroom
Finished the photoshoot with Mia
Got to the bathroom before Mia put the towel on
Chose to play with NTR when the game started
Decided on all the relationships