Both are my two favorite romantic comedies of all time with amazing acting, OSTs and love stories. Both are very touching heartwarming love stories about male leads with PTSD who push others away due to their fears of getting hurt again. In Woo Jin's case from 30b17 he thinks it's that he's afraid of hurting others again, but both are very mistaken about their traumatic incidents which the female leads help them to realize. Both female leads in their own ways haven't been able to live up to their brilliant younger selves due to life altering accidents and both shows are about how both couples help each other find the courage to live and love again. Shin Hye Sun is in my top 5 favorite actresses right up there with Gong Hyo Jin though Shin Hye Sun has only recently started getting leading roles. They are both so lovable as people and so talented as actresses. They both make me cry buckets of tears and laugh ridiculously loud and feel amazed by their talents both comedically and emotionally. They both become their characters so seamlessly that I can't wait to watch their next shows.
Both are written by the same writer with similar genre of romantic comedy. Both have Shin Hye Sun in it which show how amazingly far she's come from being a support character in one show and the main lead in the other. Also it shows her range as both characters could not be more different. Both male leads have PTSD that often interfere with their lives and the love of someone from their childhood who they didn't recognize initially brings them both out of their hard shells to help them return to who they were when they were younger. Both shows have great moments of Womance though in 30b17 the women are not love rivals. Both have a lot of humor and heart.
Both shows have very memorable characters and love stories with amazing acting. Both shows have hilariously quirky characters who are housemates, male leads with severe PTSD who find healing through his housemates and especially the female leads. Both couples have amazing chemistry in their own way though IOTL is much more mature and 30b17 is much more innocent due to their emotional ages. Both shows openly talk about going to seek psychiatric help which is very tabooed or rarely shown or talked about in Korean or Asian shows at the time of their airing.
Both shows are about a male leads debilitated by a traumatic incident where they blame themselves for what they think is the death of someone very important to them when they were younger. Both men developed severe mental disorders due to their guilt and it takes over their lives. Both female leads from both stories enter these men's lives to help them heal from their past traumas and help them overcome their guilt and see the past for what it truly was instead of what they have been thinking it was all this time. Both stories have a lot of humor and heart and have a great romantic story. Though HMKM is much more drama than comedy and 30b17 is much lighter and more comedic. Both male leads get help from a psychiatrist for their mental disorders which is very rarely shown in Korean or Asian dramas at the time of the shows' airing.
Both hilarious romantic comedies involving main characters with shared childhood traumas. Both couples don't initially know that that they had met when they were younger much less shared life changing moments with each other. Both great romances though WWWSK is much more mature and 30b17 more innocent due to the characters' emotional ages.