What I remember. Intro: MC was fat and bullied by classmates, delinquents, and relatives (step siblings?) Saves girl #1 from harrassment but gets beat up. Goes home where he lives alone, finds isekai portal to a sage's house. Equips and levels up. Goes back to Earth transformed.
Beats up some of his bullies, gets phone number from model at a photoshoot girl #2. Meets girl #1 who interferes with step siblings' bullying and she offers mc to transfer to her father's rich people high school.
Goes back to isekai. Saves a princess at outskirt of sage's forest, girk #3. Gets recognized by king, goes back to Earth but makes an appointment to meet princess again. But also meets the assassing girl #4 who targets the princess girl #3. They don't know each other but they train together in the forest.
Mc goes back to earth and impresses all his new classmates. I think model girl #2 goes to same school (?), completing the love triangle on Earth. Kills a bear with his bearly bare hands and also impresses his female teacher maybe girl #5.
Goes back to isekai to appointment with princess girl #3, and now assassin girl #4 shows up to kill princess and now the possible love triangle in isekai is set up.
Or I could be remembering everything incorrectly.